Multidirectional instability—arthroscopic treatment and outcomes

Introduction

As noted in Chapter 35 , the basic science and clinical characteristics of multidirectional instability (MDI) have helped identify this clinical entity more thoroughly. Subsequent research efforts have established a better understanding of the basis for laxity, symptomatic laxity, and reestablishing glenohumeral stability, whether through rehabilitation or open or arthroscopic surgery. This chapter is focused on the techniques and outcomes of arthroscopic capsular plication for symptomatic MDI.

The diagnosis and treatment of symptomatic MDI remain clinical challenges for the treating surgeon. To date, there are no standardized criteria by which MDI can be diagnosed. The multiple static and dynamic stabilizers including glenoid version, glenohumeral ligament integrity, and concavity compression forces, as well as the necessary balance of scapulothoracic function, rotator cuff strength, proprioception, and glenohumeral volume, all play an important role in providing stability. ^, All these factors can make the diagnosis of symptomatic MDI perplexing at best and contribute to the difficulty of selecting the most appropriate and effective treatment.

Once this challenging diagnosis has been made, a conservative, nonoperative program to include activity modification and therapeutic shoulder strengthening exercises has been advocated with a modicum of success anticipated. Nyiri et al. analyzed the biomechanical effects of isolated physical rehabilitation and concluded that the exercises alone could not normalize the aberrant kinematic patterns noted in the symptomatic MDI patient. That said, Burkhead et al. reported good and excellent outcomes in more than 80% of patients with atraumatic instability treated with a conservative strengthening program. Kuroda et al. reported improvement in symptoms once rehabilitation exercises and permanent activity modifications were implemented. Watson et al. recently reported on the success of a very specific rehabilitation protocol for symptomatic MDI patients and reported significant improvements in strength and other outcome measures after a well-supervised 3-month program. A recent study by Kiss et al. followed symptomatic MDI patients undergoing nonoperative management over an average of 4 years and found that one-third of the patients still had moderate to total disability, whereas Longo et al., in a systematic review, reported that of the 253 patients who underwent rehabilitative measures, 21% required surgical intervention. It is noteworthy that in the longitudinal study by Misamore et al., those who did not respond to 3 months of conservative care were unlikely to respond to further nonoperative measures. For those who do not respond to a conservative approach, chronic pain may be the primary complaint rather than frank instability episodes. The capsular insufficiency can lead to a significant capsulitis ( Fig. 38.1 ) in addition to secondary rotator cuff symptoms. The systematic review by Warby et al. was compromised by the poor quality and bias of the available studies, leaving us without clinical recommendations and calling for more robust future investigations.

Within the literature, the concept of traumatic versus atraumatic MDI was popularized by Matsen. The mnemonics of TUBS (traumatic, unidirectional, Bankart lesion, surgery) and AMBRI (atraumatic, multidirectional, bilateral, rehabilitation, inferior capsular shift if surgery required) have become a convenient way to establish a working diagnosis. However, it is incumbent upon the clinician to consider another clinical entity in which trauma is superimposed on an asymptomatic, ligamentously lax individual. ^, This distinction is meaningful because true MDI is a capsular aberration, whereas traumatic instability has been a labral-based entity with capsular lengthening as a secondary phenomenon due to recurrences. The results from the treatment of labral-based instability are very different from pure capsular procedures, a fact that can be very hard to determine from the current literature. A clinical series that reports a high incidence of associated Bankart lesions in male patients may actually represent a traumatic-on-atraumatic patient population, and the success rates with surgery may exceed those reported for patients with global, nonlabral symptomatic instability. Although a legitimate cohort, the MDI discussed in this section is largely based on capsular rather than labral pathology ( Fig. 38.2 ), and it is generally only in longstanding cases of untreated MDI that significant labral pathology would be encountered at surgery.

The purpose of surgery when treating a symptomatic MDI patient is restoration of enough stability so that dynamic stabilizers can once again become effective, namely scapulothoracic, core rhythm and strength, proprioceptive protection, and enhanced concavity—compression from improved rotator cuff function. For capsular-based MDI, ligament and capsular tightening is an unlikely final long-term outcome (especially in patients with generalized joint laxity); however, short-term tightening may provide the proper environment for the secondary dynamic stabilizing mechanisms to be reestablished.

Outcomes and complications

Reports on the success of open inferior capsular shift in the treatment of MDI have largely been positive, and this includes the athletic population. ^, Arthroscopic capsular plication has become a reliable surgical alternative for those with recalcitrant MDI dysfunction and is the preferred approach given the unique ability to view and treat associated pathology, minimize soft tissue trauma, potentially accelerate the rehabilitation protocol, and limit functional motion loss. Furthermore, the efficacy of arthroscopic inferior capsular plication in the difficult overhead athletic population has been documented. ^, ^, ^,

The fact that the arthroscopic technique can achieve the same results as the open approach has been the focus of several investigations, including establishing that suturing to the intact labrum is comparable to use of a suture anchor and that five plication sutures capturing 1 cm of capsular tissue can provide a volume reduction of 50%, equaling that achievable in an open approach. Systematic reviews and meta-analyses have also established that the arthroscopic recurrence and complication rates as well as the return to full activities are comparable to the results reported with open surgery. ^, ^, Two of these reviews also noted the high failure rate with thermal capsulorrhaphy, a technique that has now been abandoned as a viable treatment alternative for MDI. ^, –

Among the many reports focusing on the arthroscopic treatment of MDI, a few deserve emphasis. In 1997, McIntyre et al. detailed their outcomes following arthroscopic treatment for MDI utilizing a multiple suture technique. In this study, 19 patients were followed for a minimum of 2 years, and overall 18 of 19 demonstrated excellent or good results. With respect to the patients included in the study, 10 of the 19 had labral tearing and 9 had capsular redundancy as the primary arthroscopic finding. The authors noted that 14 of 19 patients were injured playing a sport and 13 of the 16 experienced either a subluxation or frank dislocation preoperatively. This is an early example of the difficulty of interpreting studies focused on the treatment of MDI; the heterogeneous nature of the patient population and the lack of a consistent definition of MDI make the results less cogent. In this study, those with only capsular pathology had an anterior capsular plication performed with multiple sutures passed through the capsule followed by tissue shifting from front to back using a trans-glenoid drill hole. The posterior and inferior components of the capsular shift were treated in a similar fashion and the multiple sutures were brought through a drill hole in either the clavicle or scapular spine to be tied down. This novel and innovative surgical technique provided the impetus to transition to arthroscopic solutions rather than the open approach for symptomatic MDI patients.

In 1999, Treacy et al. reported their experience early in the evolution of the arthroscopic approach to MDI. Their cohort consisted of 25 patients followed for a minimum of 2 years. Although all patients exhibited a strong inferior component to their symptoms, 11 patients had an actual dislocation event preoperatively that required a physician-assisted relocation. Of these patients, 14 of the 25 patients had a Bankart lesion noted at the time of surgery; 20 of the 25 patients were male. Despite utilizing a trans-glenoid technique, which would be considered nonanatomic by current standards, their success rate was 88%, with 3 of 25 patients demonstrating recurrent instability. The successful outcome in this series again highlights the difficulties of analyzing the surgical outcomes for MDI given the high percentage of Bankart lesions and the largely male population. One might conclude that up to 50% of this patient population represented a traumatic instability history superimposed on a background ligamentous laxity, and comparisons to MDI investigations in which minimal labral pathology is expected can be challenging to decipher.

Conversely, Jones et al. reported on arthroscopic capsular plication in overhead athletes with the diagnosis of microtraumatic anterior shoulder instability. The study included 20 overhead athletes (13 female) who did not respond to nonoperative measures; at an average of 43 months postoperatively, 90% had returned to their overhead sport. Of those who returned to sport, 85% did so at the same preoperative proficiency level. Within this cohort, no significant Bankart pathology was noted at the time of surgery; however, 20% had articular-sided partial rotator cuff injuries, which were debrided. All patients were noted to have a positive drive-through sign and a grade II or greater anterior laxity with stress testing. There were no preoperative dislocations recorded for the patients included in this study. Although the characteristics of this cohort are more consistent with the capsular pathology of MDI, the very limited scope of the laxity in this study, namely the anterior-inferior capsular lengthening caused by repetitive stress in the overhead athlete, makes these results less applicable to the challenging MDI patient with global laxity.

Highlighting the fact that it is difficult to find a study that appropriately captures the MDI patient with global laxity, Fleega et al. published on their technique in which an arthroscopic L-type capsular shift was performed and was based on the humeral attachment, much like the original open shift described by Neer. ^, Of the 108 consecutive patients treated with this approach, 71% (77 of 108) had a history of microtraumatic capsular compromise without a single traumatic event or major injury. Of note, 25 of the 108 patients (23%) had a Bankart lesion at the time of surgery and were eliminated from the cohort. Another 8 patients had an “open” rotator interval and were excluded. In this study, 75 patients met the inclusion criteria and were followed for an average of 7 years. Of the included patients, 65% were male, and the average age was 31 years. However, all of the patients reported a history of shoulder dislocation (ranging from 3 to 11 episodes), whereas only 30% met the preoperative criteria for ligamentous laxity. Postoperatively, American Shoulder and Elbow Surgeons (ASES) scores, constant values, and the University of California Los Angeles (UCLA) metrics all demonstrated statistically significant improvements without motion loss. Although the inclusion criteria were more stringent in this study with respect to the absence of Bankart lesions, the limited anterior-inferior instability profile, the preponderance of men versus women, and the history of frank dislocation in every patient may lead one to conclude that this paper does not reflect the symptomatic, global MDI patient.

The most recent investigation evaluating the efficacy of arthroscopic capsular plication for MDI was the work provided by Witney-Lagen et al., whose inclusion criteria were the most favorable for establishing a nonlabral, global instability patient cohort. In this study, 50 consecutive plications were performed in patients who did not respond to at least 6 months of conservative treatment. No patient required a shoulder reduction, as all subluxation or dislocation episodes were self-correcting. Patients with labral lesions including superior labrum anterior posterior (SLAP lesions) pathology were excluded from the study group. No patient younger than 16 years was included, and no structural abnormalities were noted on preoperative magnetic resonance imaging. Of the patients included, 5 of 50 had additional rotator interval closure if the drive-through sign was still present after the plication. A minimum 2-year follow-up was required, with an average of 5 years. The mean age of the patient was 26 years old, 32 of the 50 were male, and 11 of 50 had Beighton scores greater than 4 (mean score was 3). In this population, two recurrences were noted and 47 of the 50 patients were satisfied. Those with higher preoperative Beighton scores fared worse postoperatively. All patients in the study returned to work, and 90% returned to their sports at the same level.

Given the generally positive results that have been reported after arthroscopic surgical intervention for the symptomatic MDI patient, selecting those patients eligible for operative management may be the most demanding task required of the treating clinician. The following section outlines the surgical technique in detail.

Authors’ preferred surgical technique: Arthroscopic capsular plication

Preoperative work-up and indications for arthroscopic capsular plication

As noted earlier, the surgical candidate for treatment of symptomatic MDI exhibits the hallmarks of the ailment, including physical findings that establish generalized ligamentous laxity; positive diagnostic imaging, usually consisting of an MR arthrogram revealing capsular redundancy; and a failure to respond to a robust, supervised shoulder rehabilitation program focusing on proprioception, scapular stabilization, and rotator cuff strengthening while modifying activities. Those individuals who remain symptomatic after a 6-month course of treatment would be considered surgical candidates. Although functional loss alone can be considered an indication for surgery, pain is usually the primary factor that drives patients to seek a more aggressive treatment alternative.

Set-up and positioning

The patient undergoes an examination under general anesthesia (EUA), and the preoperative assessment is confirmed or modified. The EUA should be performed in the supine position so that a comparison to the contralateral extremity can be evaluated. The scapula must be stabilized for the exam to be meaningful. Although the EUA may show either or both anterior-posterior instability, inferior instability is a required cardinal feature of MDI. If it is not present, the diagnosis should be in doubt. Other signs of ligamentous laxity are often present, such as a positive metacarpal phalangeal hyperextension past 90 degrees ( Fig. 38.3 ) as described by Beighton et al. For the arthroscopic portion of the examination, the lateral decubitus position is the preferred position as it permits a better and more ergonomically efficient approach to the inferior and posterior capsule.

Portal placement

A modified posterior portal (MPP) is placed slightly more lateral than the typical location so that the glenoid rim does not limit the instrumentation. Diagnostic arthroscopy is then undertaken to assess any concomitant pathology. The rotator interval is often noted to be patulous, whereas the articulating surfaces and rotator cuff are typically intact. In cases of global MDI, the labrum is intact or perhaps slightly frayed as would be anticipated with a primarily capsular abnormality. As noted earlier, labral tearing may be encountered in longstanding, untreated cases. A markedly positive drive-through sign is typically encountered ( Fig. 38.4 ). Dual anterior portals are established with the anteroinferior portal (AIP) abutting the leading edge of the subscapularis and the anterosuperior portal (ASP) is placed at the most cephalad aspect of the rotator interval ( Fig. 38.5 ).