Biomechanics of the Acute Boutonniere Deformity

Lambda Repair: A Novel Repair Technique for Chronic Boutonnière Deformity

SUMMARY

Correction of a boutonnière deformity is one of the most demanding challenges in hand surgery. Surgical interventions are usually considered when functional use of the finger cannot be obtained after intense hand therapy. The authors introduce their newly described lambda (λ) repair, which is an easy-to-learn, straightforward surgical technique. The method involves an end-to-side tenorrhaphy of the lateral bands, resembling the Greek λ. Patients who underwent a lambda repair were retrospectively evaluated with preoperative and postoperative measurements of proximal interphalangeal (PIP) joint movement. Four patients (two male, two female; median age, 35.5 years) with a median follow-up period of 9.1 months were included. Three patients underwent lambda repairs for isolated boutonnière deformities, and one patient received a vascularized free toe transfer combined with a lambda repair. The preoperative average PIP joint extension lag or deficit was 28.75 degrees and could be reduced to 15 degrees. Preoperative average PIP joint active flexion was 60 degrees, which was improved to 88.75 degrees. No complications were observed. The lambda repair is a new tool in the reconstruction of boutonnière deformity, further expanding the armamentarium of hand surgeons.

The relative motion concept in acute and chronic boutonniere deformity: Invited commentary

STUDY DESIGN

Retrospective.

INTRODUCTION

Boutonniere deformity (BD) is a troublesome injury occurring from rupture of tissue connecting the extrinsic to intrinsic tendon systems. This causes loss of interphalangeal joint balance, and immobilization often results in adherence and difficulty restoring balance.

PURPOSES

Review of relative motion flexion (RMF) orthotic use for safe healing during functional activity in 23 patients, and explanation of the rationale.

METHODS

Anatomic rationale and clinical experience is reviewed in 8 acute BD patients utilizing RMF orthoses for 6 weeks, and for chronic BD patients, 3 months after serial casting.

RESULTS

All patients met the Strickland and Steichen criteria for "excellent" results following treatment, with an average of 35° increase in ROM.

DISCUSSION

The anatomic rationale for relative motion recognizes that altering relative positioning between adjacent metacarpophalangeal (MCP) joints produces a protective favorable impact on interphalangeal forces during hand function using 15°-20° greater MCP joint flexion. This provides dorsal and volar protective benefits because the extensor digitorum communis (EDC), a single-muscle-four-tendon system, attaches to the intrinsic lateral band (LB) tendons. With greater MCP flexion, dorsal EDC force is increased, pulling lateral bands medially, while on the volar surface the downward pull of the lumbrical on LB is relaxed due to origin from the flexor digitorum profundus tendon of the injured digit, also a single-muscle-four-tendon system. The RMF orthosis permits protected active motion during functional activity with acute BD. In patients with chronic BD and adequate passive extension, an RMF orthosis for 3 months also produced encouraging results.

CONCLUSION

Management of acute BD with RMF orthoses provided earlier recovery of motion and hand function. Similar results occurred for chronic BD using serial casting for adequate extension followed by 3 months of RMF orthotic use and should be attempted prior to surgical intervention, with surgery remaining an alternative.

An in-depth look at zone III and IV anatomy of the finger extensor mechanism and some clinical implications for use of the relative motion flexion orthosis

BACKGROUND

For hand therapists and hand surgeons acute and chronic injuries of the extensor mechanism (EM) in zones III-IV are challenging to treat with satisfying results.

INTRODUCTION

Early active motion combined with relative motion flexion (RMF) orthoses to manage EM zone III injuries and boutonnière deformity has renewed interest in the complex anatomy and biomechanics of the EM.

PURPOSE

To provide an in-depth discussion of EM zones III-IV anatomy with emphasis on inter-tendinous structures, often omitted in simplified, model-wise illustrations which focus mostly on the tendinous structures.

METHOD

In collaboration the authors combined on the one hand extensive clinical experience and knowledge of the EM literature and on the other hand decades of anatomical, biomechanical and kinesiology research of the EM with special interest for the spiral fibers, through gross anatomy and microdissection anatomy laboratory work, MRI and ultrasonography studies.

RESULTS

The inter-tendinous tissues (i.e., spiral fibers) in zone III are of imminent importance for proper functioning of the EM and to prevent boutonnière deformity to develop after EM surgery or injury.

DISCUSSION

Inter-tendinous links between the tendinous structures of the EM are necessary for balanced finger motion. The spiral fibers are described in more detail because of their role in controlling volar migration of the conjoined lateral bands and because their disruption makes development of boutonnière deformity more likely. Understanding the anatomy and biomechanics of the EM may assist in progress toward 'proof of concept' for use of RMF orthoses and controlled early active motion after EM injury or surgery.

CONCLUSION

Hand surgery and hand therapy practice interventions, including use of RMF orthoses for management of non-surgical and surgical EM injuries may benefit from an in-depth look at the EM zone III and IV anatomy and biomechanics.

Use of a relative motion flexion orthosis with dorsal hood to protect a middle phalanx finger fracture and zone III extensor tendon repair, while correcting a secondary fixed flexion proximal interphalangeal joint flexion contracture: A case report

BACKGROUND

Proximal interphalangeal joint (PIPJ) contractures, zone III extensor tendon injuries and phalanx fractures are challenging to treat in isolation. In this case the patient presented with all 3 of these issues in a single digit, presenting a unique problem for the hand therapist.

PURPOSE

A case report to examine the effectiveness of using single orthosis to treat an index finger following a combined zone III extension tendon repair, surgically stabilized second phalanx fracture and PIPJ flexion contracture.

METHODS

A patient presented to therapy with a 40° PIPJ flexion contracture and minus 70° of active PIPJ extension (ICD10 M25.64) after left index surgical fixation of a middle phalanx fracture (ICD10 S62.621B) and zone III extensor tendon repair (ICD10 S66.321A). To correct the contracture, a distal elastic strap was added to a relative motion flexion orthosis with dorsal hood. This applied a gentle extension force to the PIPJ. Once the contracture resolved a short arc motion program (SAM) was initiated using the same orthosis.

RESULTS

At 20 weeks post initial therapy evaluation, active range of motion (extension/flexion) of the PIPJ was 5°/100° and distal interphalangeal joint (DIPJ) 0°/60°. The Quick DASH score improved 50 points from an initial 59 points to 9 points. The patient reported good satisfaction and full function of the hand.

CONCLUSION

Our case report demonstrated the effective use of a single relative motion flexion orthosis with a dorsal hood when treating a complex hand injury involving an open zone III injury, second phalanx fracture and 40-degree PIPJ contracture.

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

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.

[Extensor tendon injuries at the level of the proximal interphalangeal joint]

Closed and open injuries of the extensor mechanism at the proximal interphalangeal (PIP) joint can involve the central slip, the lateral slips or both. They are classified as zone III injuries. All open injuries on the dorsal side of the PIP joint should raise suspicion of an extensor tendon injury that is frequently overlooked. The operative strategy consists of wound revision with extensor tendon suture or refixation of the central slip. Acute closed central slip injuries are clinically diagnosed (Elson test) after ruling out bony injuries to the joint. Nondisplaced avulsions of the central slip insertion or lacerations can be treated nonoperatively by splinting. For displaced avulsions and complex injuries the treatment is surgical. In overlooked injuries a typical deformity (buttonhole/Boutonnière deformity) develops within 1-2 weeks that is characterized by an extension lag of the PIP joint and hyperextension at the distal interphalangeal joint. In early cases, when passive extension is still complete (mobile buttonhole deformity) the central slip can be immediately reconstructed. In fixed deformities complete passive extension of the PIP joint has to be restored before surgery by hand therapeutic measures or PIP joint release. Depending on the pattern of the injury and the resulting defects, a number of reconstructive techniques have been established that are summarized in this article. The functional results can be limited by tendon adhesions, imbalance within the reconstructed extensor apparatus and stiff joints that can all restrict the range of motion. Therefore, active rehabilitation protocols are mandatory for optimal results.

Extension Mechanism of the Proximal Interphalangeal Joint of the Human Phalanx: A Cadaveric Biomechanical Study

Our purpose was to compare the contributions of these two systems to assess PIP joint extension in fresh cadaver models. Nine middle fingers of fresh cadavers were used. The PIP joint angle was measured while an extension load was applied on the extensor tendons. Specimens on which extension load was applied on the extrinsic extensors were classified as the extrinsic group, and those on which extension load was applied on the intrinsic extensors were classified as the intrinsic group. Linear regression analyses were performed to obtain regression equation and the extension load-PIP joint angle curve. The mean of slope of the curve was compared between the two groups using paired t-test. The same experiments were done for the metacarpophalangeal (MP) joint in 0° and 60° flexion to evaluate the effect of MP joint flexion on PIP joint extension. The mean slope of the extension load-PIP joint angle curve of the extrinsic group was significantly greater than that of the intrinsic group. With the MP joint in 0° flexion, the mean slope of the extrinsic and intrinsic groups was -0.148 and -0.117, respectively (greater absolute value means greater slope, p = 0.01). With the MP joint in 60° flexion, the mean slopes were -0.147 and -0.104, respectively (p = 0.015). The contribution of the intrinsic extensor for PIP joint extension shows decreasing trends with MP joint flexion. The extrinsic extensors have greater contribution for PIP joint extension compared with the intrinsic extensors.