Advertisement

Central Slip Reconstruction With a Distally Based Flexor Digitorum Superficialis Slip: A Biomechanical Study

Published:October 23, 2021DOI:https://doi.org/10.1016/j.jhsa.2021.09.010

      Purpose

      The ideal method of central slip reconstruction is difficult to determine due to the multitude of techniques, nonstandardized outcome reporting, and small patient series in the literature. Although most boutonniere deformities may be treated with nonsurgical measures, chronic, subacute, or open injuries may require operative intervention. To aid surgeons in the choice of the ideal central slip reconstruction method, this biomechanical study compared the 3 most common methods performed at our institution: direct repair, lateral band centralization, and distally-based flexor digitorum superficialis (FDS) slip repair.

      Methods

      A boutonniere deformity was induced in 35 fresh-frozen cadaver digits. The central slip was repaired in 9 digits using a primary suture repair, in 9 digits using a lateral band centralization technique, and in 9 digits using a distally-based FDS slip reconstruction. A control group without injury was tested in 8 digits. Following repair or reconstruction, each digit was tested for load to failure, strain, and stiffness at the repair.

      Results

      The average load to failure after central slip reconstruction was significantly greater for a distally based FDS slip method at 82.1 ± 14.6 N (95% CI, 62.2–101.9 N) than all other repair types. Although the FDS slip reconstruction was not as strong as the intact state (82.1 N vs 156.2 N, respectively), it was 2.6 times stronger than the lateral band centralization (82.1 N vs 31.6 N, respectively) and 3 times stronger than a primary repair (82.1 N vs 27.6 N, respectively).

      Conclusions

      Reconstruction of the central slip using a distally-based FDS slip provided the greatest biomechanical strength compared with the direct repair or lateral band centralization.

      Clinical relevance

      The use of a distally based reconstruction using FDS may allow for safer early motion.

      Key words

      Posttraumatic central slip injuries complicated by boutonniere deformity continue to be a challenge for hand surgeons. Fabricating an orthosis of the proximal interphalangeal (PIP) joint in extension with active distal interphalangeal (DIP) joint exercises typically allows for acceptable nonsurgical management of closed injuries.
      • Strauch R.J.
      Extensor tendon injury.
      Untreated injuries with volar migration of the lateral bands result in the classically described deformity of PIP joint flexion and DIP joint hyperextension and can be associated with pain and disability.
      • Grau L.
      • Baydoun H.
      • Chen K.
      • Sankary S.T.
      • Amirouche F.
      • Gonzalez M.H.
      Biomechanics of the acute boutonniere deformity.
      ,
      • Souter W.A.
      The problem of boutonniere deformity.
      However, in case of delayed treatments, open injuries, or large bony avulsions, operative management may be warranted.
      • Strauch R.J.
      Extensor tendon injury.
      ,
      • Chan J.C.Y.
      • Purcell E.M.
      • Kelly J.L.
      Surgical repair of central slip avulsion injuries with Mitek bone anchor—retrospective analysis of a case series.
      ,
      • Feuvrier D.
      • Loisel F.
      • Pauchot J.
      • Obert L.
      Emergency repair of extensor tendon central slip defects with Oberlin’s bypass technique: feasibility and results in 4 cases with more than 5 years of follow-up.
      Although many techniques for reconstruction of the central slip of the extensor mechanism have been described, the literature remains indefinite regarding a superior technique in case of subacute or chronic injuries.
      • Geoghegan L.
      • Wormald J.C.R.
      • Adami R.Z.
      • Rodrigues J.N.
      Central slip extensor tendon injuries: a systematic review of treatments.
      ,
      • To P.
      • Watson J.T.
      Boutonniere deformity.
      Although acute lacerations without loss of substance are generally amenable to direct suture repair, little evidence is available to aid surgeons in the choice of the ideal reconstructive technique for acute cases with tendon loss or subacute or chronic deformity.
      • Strauch R.J.
      Extensor tendon injury.
      ,
      • Geoghegan L.
      • Wormald J.C.R.
      • Adami R.Z.
      • Rodrigues J.N.
      Central slip extensor tendon injuries: a systematic review of treatments.
      ,
      • Ahmad F.
      • Pickford M.
      Reconstruction of the extensor central slip using a distally based flexor digitorum superficialis slip.
      Reconstructive techniques that have been described include direct repair, interposition tendon grafting, capsule imbrication, transposition of the lateral bands, transverse retinacular ligament reconstruction, and distal extensor tenotomy.
      • Feuvrier D.
      • Loisel F.
      • Pauchot J.
      • Obert L.
      Emergency repair of extensor tendon central slip defects with Oberlin’s bypass technique: feasibility and results in 4 cases with more than 5 years of follow-up.
      ,
      • Ahmad F.
      • Pickford M.
      Reconstruction of the extensor central slip using a distally based flexor digitorum superficialis slip.
      • Matev I.
      Transposition of the lateral slips of the aponeurosis in treatment of long-standing “boutonni'ere deformity” of the fingers.
      • Patel S.S.
      • Singh N.
      • Clark C.
      • Stone J.
      • Nydick J.
      Reconstruction of traumatic central slip injuries: technique using a slip of flexor digitorum superficialis.
      • Urbaniak J.R.
      • Hayes M.G.
      Chronic boutonniere deformity—an anatomic reconstruction.
      Outcomes of central slip reconstruction have included heterogeneous patient samples in small, nonrandomized studies blending numerous techniques.
      • Chan J.C.Y.
      • Purcell E.M.
      • Kelly J.L.
      Surgical repair of central slip avulsion injuries with Mitek bone anchor—retrospective analysis of a case series.
      ,
      • Cluett J.
      • Milne A.D.
      • Yang D.
      • Morris S.F.
      Repair of central slip avulsions using Mitek Micro Arc bone anchors. An in vitro biomechanical assessment.
      ,
      • Li Y.
      • Ding A.
      • He Z.
      • Xue F.
      Comparison of proximal turndown of central slip combined with suture of lateral bands versus free tendon grafting for central slip reconstruction after an open finger injury.
      Tendon adhesions and joint stiffness being the most common complications following reconstruction, initial repair strength is critical for early range of motion.
      • Ahmad F.
      • Pickford M.
      Reconstruction of the extensor central slip using a distally based flexor digitorum superficialis slip.
      ,
      • Evans R.B.
      Early active short arc motion for the repaired central slip.
      • Lee S.K.
      • Dubey A.
      • Kim B.H.
      • Zingman A.
      • Landa J.
      • Paksima N.
      A biomechanical study of extensor tendon repair methods: introduction to the running-interlocking horizontal mattress extensor tendon repair technique.
      • Merritt W.H.
      Relative motion splint: active motion after extensor tendon injury and repair.
      The purpose of our study was to determine the difference in the biomechanical strength among the 3 common surgical techniques: direct repair, lateral band centralization, and distally-based flexor digitorum superficialis (FDS) slip repair.
      We hypothesized that the distally based FDS slip repair has superior tensile strength compared with the direct suture repair and lateral band centralization techniques. Determining the technique with the highest load to failure, cycles to failure, and least tendon displacement is critical in determining the strategy that can result in an earlier range of motion, which has been linked to better outcomes in other tendon repair/reconstructions.

      Materials and Methods

      Thirty-five fresh-frozen cadaver index, middle, ring, and little digits were obtained and thawed to room temperature. Using the largest SD previously reported in the literature for extensor tendon repair (13.88 N), a type I error of 0.05, and power of 0.9 sample, 8 digits were required for each treatment arm to detect a difference in load to failure with 25 N, the force of physiologic loading, according to a size estimation.
      • Mercer D.
      • Fitzpatrick J.
      • Firoozbakhsh K.
      • Carvalho A.
      • Moneim M.
      Extensor tendon repair with and without central slip reattachment to bone: a biomechanical study.
      ,
      • Uludağ A.
      • Tosun H.B.
      • Çelik S.
      • et al.
      Comparison of various tendon repair techniques in extansor zone 3 injuries: an experimental biomechanical cadaver study.
      All PIP joints had the full range of passive motion prior to dissection. All 3 techniques were performed by the same surgeon (J.I.M.) using a 2.5× loupe magnification. Each hand was disarticulated at the carpometacarpal joints leaving the fingers and palm intact. The extrinsic extensor tendons were preserved to the proximal edge of the extensor retinaculum and separated from the surrounding tissue. Attachments from the extrinsic extensor tendon to the dorsal base of the proximal phalanx were released in all digits. The central slip was incised 1 cm from the insertion on the middle phalanx. Additionally, the triangular ligament and interconnecting fibers of the central slip and lateral bands were incised in a standardized fashion to simulate an acute boutonniere deformity (Fig. 1). Each digit was randomly assigned to 1 of the 3 reconstruction/repair techniques or to a control group (intact tendon) using a random number generator based on the type of digit (index, middle, ring, or little) ensuring an equal distribution of digit type within each treatment arm.
      Figure thumbnail gr1
      Figure 1A Iatrogenic boutonniere deformity created by incising the central slip and triangular ligament. B Tension of extrinsic tendons does not extend the PIP joint.
      One technique involved primary repair of an acute laceration made in the central slip tendon using 2 4-0 nonabsorbable sutures in a figure-of-eight fashion (9 digits total) (Fig. 2). The second technique involved lateral band centralization as originally described by Matev
      • Matev I.
      Transposition of the lateral slips of the aponeurosis in treatment of long-standing “boutonni'ere deformity” of the fingers.
      (9 digits total) using 2 4-0 nonabsorbable sutures in a figure-of-eight fashion at each lateral band tenorrhaphy. The third technique included a distally based FDS slip reconstruction as previously described by Ahmad and Pickford
      • Ahmad F.
      • Pickford M.
      Reconstruction of the extensor central slip using a distally based flexor digitorum superficialis slip.
      (9 digits total).
      • Patel S.S.
      • Singh N.
      • Clark C.
      • Stone J.
      • Nydick J.
      Reconstruction of traumatic central slip injuries: technique using a slip of flexor digitorum superficialis.
      This technique was performed with a preferred modification using a side-to-side tenorrhaphy with Krackow suture instead of a Pulvertaft weave. A 4-0 nonabsorbable suture was used. A control group without central slip injury was also tested (8 digits total after 1 specimen was noted to be of poor quality for testing).
      Figure thumbnail gr2
      Figure 2The 3 tested reconstructive techniques. A A primary repair using 2 figure-of-eight 4-0 suture knots. B A traditional Matev central slip reconstruction using the lateral bands. C Central slip reconstruction using a slip of the FDS routed through a bone tunnel in the middle phalanx.
      Following all repair techniques except the lateral band centralization, the lateral bands were transected distal to the central slip such that testing was isolated through the central slip repair or reconstruction only. Each specimen was loaded in the Mecmesin tensile testing machine (Mecmesin Ltd) clamped by the distal phalanx. Longitudinal force was applied to a standardized length of the extrinsic extensor tendon for each digit, similar to Mercer et al
      • Mercer D.
      • Fitzpatrick J.
      • Firoozbakhsh K.
      • Carvalho A.
      • Moneim M.
      Extensor tendon repair with and without central slip reattachment to bone: a biomechanical study.
      (Fig. 3). The initial 10 cycles were performed at 30 mm/min from 0 N to 10 N followed by 30 mm/min until failure. The load to failure (N), stiffness (N/mm), and strain were recorded using a linear variable differential transformer. The linear variable differential transformer was able to measure the load to failure and stiffness with variable displacement at the repair site to evaluate whether trends in repair strength continue to be consistent as the repair failed. Dependent variables were evaluated at specific repair site displacement intervals up to a gapping of 3 mm, which has been considered clinically important in other tendon repair literature.
      Figure thumbnail gr3
      Figure 3Biomechanical testing of the central slip reconstruction. Clamps are applied to the distal phalanx of the digit and to the proximal extrinsic extensor tendon at a standardized distance.
      The normality of these data was tested using visual methods, including quantile-quantile plots and histograms, and all variables followed a normal distribution. Data were described using mean and 95% CI. Statistical comparisons between repair methods were made using analysis of variance tests with a least square means test and Tukey adjusted P values for multiple comparisons.

      Results

      The average load to failure for each reconstructive method and the control group is given in Table 1. The FDS slip reconstruction was significantly stronger with higher load to failure than the lateral band centralization (P < .05) and the primary repair (P < .05). The strongest reconstruction was the distally-based FDS slip reconstruction with an average load to failure of 82.1 N (95% CI, 62.2 N, 101.9 N). This reconstruction was 2.6 times stronger than the lateral band centralization (31.6 N; 95% CI, 12.9 N, 50.3 N) and 3 times stronger than the primary repair (27.6 N; 95% CI, 8.9 N, 46.3 N). Although the FDS slip reconstruction was significantly weaker than the intact state (156.2 N; 95% CI, 136.9 N, 176.1 N; P < .05), it was significantly stronger than the other repair methods even up to 3 mm of displacement (P < .05) (Fig. 4).
      Table 1The Average Load to Failure (N) for Each Repair Method and the Associated 95% CI
      P values are reported relative to the FDS slip repair method.
      Repair MethodAverage Load to Failure (N)

      Mean (95% CI)
      P Value
      Intact tendon (control)156.2 (126.4, 176.1)<.05
      Primary repair27.6 (8.9, 46.3)<.05
      Lateral band/Matev31.6 (12.9, 50.3)<.05
      FDS slip82.1 (62.2, 101.9)
      P values are reported relative to the FDS slip repair method.
      Figure thumbnail gr4
      Figure 4Average load to failure of each repair method with displacement up to 3 mm at the repair site. The FDS slip repair was stronger than other repair types at all displacements.
      The stiffness of the FDS slip reconstruction was the highest of all repair methods at the load to failure (Table 2) and at all levels of displacement (Fig. 5). Primary repair and lateral band centralization were not significantly different in average stiffness (P = .90). Most specimens failed at the repair site, although 2 of the specimens repaired using FDS reconstruction failed by the pull through of tendon through the bone proximal to the drill hole.
      Table 2The Average Stiffness (N/mm) of Each Repair Method Measured at the Ultimate Load and Each Associated 95% CI
      P values are reported relative to the FDS slip repair method.
      Repair MethodAverage Stiffness (N/mm)

      Mean (95% CI)
      P Value
      Primary repair32.3 (8.2, 56.3)<.05
      Lateral band/Matev24.8 (0, 50.3)<.05
      FDS slip95.2 (62.9, 127.4)
      P values are reported relative to the FDS slip repair method.
      Figure thumbnail gr5
      Figure 5The average stiffness (N/mm) measured for each repair method at multiple levels of displacement. Notably, the FDS slip repair is stiffer than all other repair sites regardless of the displacement.

      Discussion

      In this study, we compared the strength and stiffness following direct central slip repair, lateral band centralization, and distally-based FDS slip reconstruction technique. All 3 experimental repairs tolerated physiologic loading of 25 N.
      • Mercer D.
      • Fitzpatrick J.
      • Firoozbakhsh K.
      • Carvalho A.
      • Moneim M.
      Extensor tendon repair with and without central slip reattachment to bone: a biomechanical study.
      The reconstructive method described by Ahmad and Pickford
      • Ahmad F.
      • Pickford M.
      Reconstruction of the extensor central slip using a distally based flexor digitorum superficialis slip.
      using a distally-based FDS slip had a significantly higher average load to failure than the primary repair or lateral band centralization. This technique can be performed via a single midlateral incision without donor morbidity.
      • Ahmad F.
      • Pickford M.
      Reconstruction of the extensor central slip using a distally based flexor digitorum superficialis slip.
      ,
      • Patel S.S.
      • Singh N.
      • Clark C.
      • Stone J.
      • Nydick J.
      Reconstruction of traumatic central slip injuries: technique using a slip of flexor digitorum superficialis.
      The repaired tendons were not as strong as the intact control tendons, likely because of the relative weakness of suture fixation; the repair site was the site of disruption in the majority of the subjects and tendon rupture was the mode of failure of the intact state.
      Previously, investigators have advocated for early active motion as early as day 3 after FDS slip repair with active flexion and active-assisted extension of the PIP joint.
      • Patel S.S.
      • Singh N.
      • Clark C.
      • Stone J.
      • Nydick J.
      Reconstruction of traumatic central slip injuries: technique using a slip of flexor digitorum superficialis.
      Nighttime orthosis fabrication can be included with the PIP joint in extension for 4–6 weeks. Although the reporting of clinical outcomes is limited to small case series, previous investigators have described this surgical technique for revision or chronic cases or in primary traumatic cases with a primary tendon defect. Ahmad
      • Ahmad F.
      • Pickford M.
      Reconstruction of the extensor central slip using a distally based flexor digitorum superficialis slip.
      described the restoration of a functional PIP joint range of motion, 30° of flexion to 85° of extension, at 12 weeks after surgery in a case report of a revision central slip reconstruction with distally based FDS slip reconstruction in a patient with rheumatoid arthritis. Patel et al
      • Patel S.S.
      • Singh N.
      • Clark C.
      • Stone J.
      • Nydick J.
      Reconstruction of traumatic central slip injuries: technique using a slip of flexor digitorum superficialis.
      described a series of 6 patients with traumatic central slip reconstruction using this same technique with an average PIP joint range of motion of 27° of flexion to 80° of extension and DIP joint motion −5° of flexion to 42.5° of extension. Previous investigators have determined that for tendon transfers, at least 40–45 N force is experienced with passive and active range of motion.
      • Freehafer A.A.
      • Peckham P.H.
      • Keith M.W.
      Determination of muscle-tendon unit properties during tendon transfer.
      Although this technique is a tendon autograft procedure and not necessarily a tendon transfer, healing at the tenorrhaphy site is similar to tendon transfers and undergoes a similar postoperative protocol. Using this as a threshold, our biomechanical data support the use of early active motion following the distally-based FDS reconstruction, which has approximately double the strength required, whereas the other 2 repair methods did not exceed the typical load expected during active range of motion.
      • Evans R.B.
      Early active short arc motion for the repaired central slip.
      Other reconstructive methods for boutonniere deformity require a period of postoperative immobilization and have unpredictable outcomes.
      • To P.
      • Watson J.T.
      Boutonniere deformity.
      After central slip reconstruction using a triangular flap, Urbaniak and Hayes
      • Urbaniak J.R.
      • Hayes M.G.
      Chronic boutonniere deformity—an anatomic reconstruction.
      showed restoration of the PIP joint motion with less than 30° extension deficit in 12 of the 13 patients. Suzuki
      • Suzuki K.
      Reconstruction of post-traumatic boutonniere deformity.
      showed restoration of the full range of motion in only 27% of patients with an interposition palmaris graft and the other 73% had some or less than half the normal range of motion. A more recent modification that incorporates a palmaris longus autograft in a cross-lateral band technique led to favorable PIP joint motion restoration with less than a 7° extension deficit in a small series of 7 patients. This may have more utility in patients with deficient lateral bands.
      • Duzgun S.
      • Duran A.
      • Keskin E.
      • Yigit A.K.
      • Buyukdogan H.
      Chronic boutonniere deformity: cross-lateral band technique using palmaris longus autograft.
      The previous literature is limited in the ability to compare methods of reconstruction due to the multitude of treatment methods, nonstandardized outcome measures, small case series, and no comparison to nonsurgical treatment.
      • Geoghegan L.
      • Wormald J.C.R.
      • Adami R.Z.
      • Rodrigues J.N.
      Central slip extensor tendon injuries: a systematic review of treatments.
      ,
      • To P.
      • Watson J.T.
      Boutonniere deformity.
      The main limitation of this study is that as a biomechanical study, the reconstructive strength was simulated only at the time of surgery. We did not account for the added strength of tendinous healing, although we hypothesized that 1 tenorrhaphy site in the distal FDS slip reconstruction was more favorable than having 2 in the case of an interposition tendon graft reconstruction or lateral band centralization. Additionally, the central slip transection in this study simulates a sharp injury, although this may not be generalizable to acute avulsions or nonacute boutonniere deformities. In chronic deformity, a primary repair is rarely an option and reconstructive techniques are more frequently needed. Chronic changes at the PIP and DIP joints include joint stiffness, attenuation of surrounding ligaments, and lateral band displacement that may complicate treatment. We hypothesized that the added tendon length and strength of suture technique in the distal FDS slip reconstruction would make it effective for these injuries, although the strength added in repositioning the lateral bands, such as in the Matev technique, may be more important for these types of injuries.
      Another potential confounder of the strength comparison is that the distally based FDS slip technique was repaired with a running Krackow suture instead of 2 figure-of-eight sutures in the other groups. The benefit of the added length of graft allows for the use of a stronger suture technique for the distally-based FDS slip technique that the other techniques are not afforded. Special consideration during the preoperative examination for an FDS is important when considering this reconstructive method for the little finger. Prior literature suggests the prevalence of an absent FDS in the little finger to be 13% to 21%.
      • Townley W.A.
      • Swan M.C.
      • Dunn R.L.
      Congenital absence of flexor digitorum superficialis: implications for assessment of little finger lacerations.
      ,
      • Bowman P.
      • Johnson L.
      • Chiapetta A.
      • Mitchell A.
      • Belusko E.
      The clinical impact of the presence or absence of the fifth finger flexor digitorum superficialis on grip strength.
      Reconstruction of the central slip using a distally-based FDS slip provides the greatest biomechanical strength compared with primary repair and lateral band centralization and may be sufficient to allow earlier motion protocols.

      References

        • Strauch R.J.
        Extensor tendon injury.
        in: Wolfe S.W. Pederson W.C. Hotchkiss R.N. Kozin S.H. Cohen M.S. Green’s Operative Hand Surgery. 7th ed. Elsevier, 2017: 152-182
        • Grau L.
        • Baydoun H.
        • Chen K.
        • Sankary S.T.
        • Amirouche F.
        • Gonzalez M.H.
        Biomechanics of the acute boutonniere deformity.
        J Hand Surg Am. 2018; 43: 80.e1-80.e6
        • Souter W.A.
        The problem of boutonniere deformity.
        Clin Orthop. 1974; 104: 116-133
        • Chan J.C.Y.
        • Purcell E.M.
        • Kelly J.L.
        Surgical repair of central slip avulsion injuries with Mitek bone anchor—retrospective analysis of a case series.
        Hand Surg. 2007; 12: 29-34
        • Feuvrier D.
        • Loisel F.
        • Pauchot J.
        • Obert L.
        Emergency repair of extensor tendon central slip defects with Oberlin’s bypass technique: feasibility and results in 4 cases with more than 5 years of follow-up.
        Chir Main. 2014; 33: 315-319
        • Geoghegan L.
        • Wormald J.C.R.
        • Adami R.Z.
        • Rodrigues J.N.
        Central slip extensor tendon injuries: a systematic review of treatments.
        J Hand Surg Eur Vol. 2019; 44: 825-832
        • To P.
        • Watson J.T.
        Boutonniere deformity.
        J Hand Surg Am. 2011; 36: 139-142
        • Ahmad F.
        • Pickford M.
        Reconstruction of the extensor central slip using a distally based flexor digitorum superficialis slip.
        J Hand Surg Am. 2009; 34: 930-932
        • Matev I.
        Transposition of the lateral slips of the aponeurosis in treatment of long-standing “boutonni'ere deformity” of the fingers.
        Br J Plast Surg. 1964; 17: 281-286
        • Patel S.S.
        • Singh N.
        • Clark C.
        • Stone J.
        • Nydick J.
        Reconstruction of traumatic central slip injuries: technique using a slip of flexor digitorum superficialis.
        Tech Hand Up Extrem Surg. 2018; 22: 150-155
        • Urbaniak J.R.
        • Hayes M.G.
        Chronic boutonniere deformity—an anatomic reconstruction.
        J Hand Surg Am. 1981; 6: 379-383
        • Cluett J.
        • Milne A.D.
        • Yang D.
        • Morris S.F.
        Repair of central slip avulsions using Mitek Micro Arc bone anchors. An in vitro biomechanical assessment.
        J Hand Surg Br. 1999; 24: 679-682
        • Li Y.
        • Ding A.
        • He Z.
        • Xue F.
        Comparison of proximal turndown of central slip combined with suture of lateral bands versus free tendon grafting for central slip reconstruction after an open finger injury.
        Acta Orthop Belg. 2014; 80: 119-125
        • Evans R.B.
        Early active short arc motion for the repaired central slip.
        J Hand Surg Am. 1994; 19: 991-997
        • Lee S.K.
        • Dubey A.
        • Kim B.H.
        • Zingman A.
        • Landa J.
        • Paksima N.
        A biomechanical study of extensor tendon repair methods: introduction to the running-interlocking horizontal mattress extensor tendon repair technique.
        J Hand Surg Am. 2010; 35: 19-23
        • Merritt W.H.
        Relative motion splint: active motion after extensor tendon injury and repair.
        J Hand Surg Am. 2014; 39: 1187-1194
        • Mercer D.
        • Fitzpatrick J.
        • Firoozbakhsh K.
        • Carvalho A.
        • Moneim M.
        Extensor tendon repair with and without central slip reattachment to bone: a biomechanical study.
        J Hand Surg Am. 2009; 34: 108-111
        • Uludağ A.
        • Tosun H.B.
        • Çelik S.
        • et al.
        Comparison of various tendon repair techniques in extansor zone 3 injuries: an experimental biomechanical cadaver study.
        Arch Orthop Trauma Surg. 2020; 140: 583-590
        • Freehafer A.A.
        • Peckham P.H.
        • Keith M.W.
        Determination of muscle-tendon unit properties during tendon transfer.
        J Hand Surg Am. 1979; 4: 331-339
        • Suzuki K.
        Reconstruction of post-traumatic boutonniere deformity.
        Hand (N Y). 1973; 5: 145-148
        • Duzgun S.
        • Duran A.
        • Keskin E.
        • Yigit A.K.
        • Buyukdogan H.
        Chronic boutonniere deformity: cross-lateral band technique using palmaris longus autograft.
        J Hand Surg Am. 2017; 42: 661.e1-661.e5
        • Townley W.A.
        • Swan M.C.
        • Dunn R.L.
        Congenital absence of flexor digitorum superficialis: implications for assessment of little finger lacerations.
        J Hand Surg Eur Vol. 2010; 35: 417-418
        • Bowman P.
        • Johnson L.
        • Chiapetta A.
        • Mitchell A.
        • Belusko E.
        The clinical impact of the presence or absence of the fifth finger flexor digitorum superficialis on grip strength.
        J Hand Ther. 2003; 16: 245-248