Rotator Cuff Repair Surgery Research Articles

Fatality Involving Complications of Bupivacaine Toxicity and Hypersensitivity Reaction*

This case represents unusual findings of elevated bupivacaine and tryptase concentrations following local anesthetic, bupivacaine, administered as a scalene nerve block for elective rotator cuff repair surgery. Following bupivacaine injection, the patient exhibited almost immediate seizure activity, bradycardia, and cardiac arrest. Resuscitative efforts including cardiopulmonary bypass restored a cardiac rhythm. However, the clinical medical status of the patient progressively declined and he died 7 h following administration of the local anesthetic. Autopsy revealed several abnormalities of the heart including cardiomegaly, myocardial bridging, and lipomatous hypertrophy of the intraatrial septum, which may have contributed to bradycardia and arrhythmia. Postmortem toxicology results revealed elevated bupivacaine and tryptase concentrations. Elevated postmortem bupivacaine concentrations 7 h following administration and abrupt onset of seizures indicate unintentional intravascular injection instead of nerve and tissue infiltration. An elevated postmortem tryptase concentration points to the possibility of a hypersensitivity reaction to bupivacaine.

Postural dependence of passive tension in the supraspinatus following rotator cuff repair: A simulation analysis

BackgroundDespite surgical advances, repair of rotator cuff tears is associated with 20–70% incidence of recurrent tearing. The tension required to repair the torn tendon influences surgical outcomes and may be dependent on the gap length from torn tendon that must be spanned by the repair. Detailed understanding of forces throughout the range of motion (ROM) may allow surgeons to make evidence-based recommendations for post-operative care. MethodsWe used a computational shoulder model to assess passive tension and total moment-generating capacity in supraspinatus for repairs of gaps up to 3cm throughout the shoulder (ROM). FindingsIn 60° abduction, increased gap length from 0.5cm to 3cm caused increases in passive force from 3N to 58N, consistent with those seen during clinical repair. For reduced abduction, passive forces increased substantially. For a 0.5cm gap, tension throughout the ROM (elevation, plane of elevation, and rotation) is within reasonable limits, but larger gaps are associated with tensions that markedly exceed reported pull-out strength of sutures and anchors. Peak moment for a large 3cm gap length was 5.09Nm, a 53% reduction in moment-generating capacity compared to uninjured supraspinatus. InterpretationWe conclude that shoulder posture is an important determinant of passive forces during rotator cuff repair surgery. Choosing postures that reduce forces intraoperatively to permit repair of larger gaps may lead to failure postoperatively when the shoulder is mobilized. For larger defects, loss of strength in supraspinatus may be substantial following repair even if retear is prevented.

Arthroscopic Techniques in Minimally Invasive Spine Surgery: Closure of the Lumbar Fascia: Surgical Technique

The constrained working area in minimally invasive exposures of the spine may limit the capacity to effectively close the lumbar fascia, especially in patients with elevated body mass indexes. The working channel in these cases may have a diameter as narrow as 14 mm and a length up to 9 cm. Under these circumstances, the use of a conventional needle driver and a curved needle becomes suboptimal for closures of the fascia. To demonstrate the utility of an arthroscopic suture passer for closure of the lumbar fascia in such approaches. A flexible suture passer, typically used in arthroscopic rotator cuff repair surgery, was used through a minimally invasive portal for fascial closure after minimally invasive lumbar spine procedures. The use of an arthroscopic suture passer precludes the need for rotation of a curved needle in a constrained working area. Deploying a nitinol needle through an arc delivers the suture through the fascia, thereby facilitating closure. Satisfactory lumbar fascia closures were achieved in 18 patients with elevated body mass indexes. Application of existing technology in other surgical specialties may address the shortcomings of current techniques in minimally invasive approaches to the spine. The use of a flexible arthroscopic suture passer is one example in which current technology in one discipline may be applied to minimally invasive approaches. Increasing the awareness of techniques and instruments in other surgical disciplines may expand the armamentarium of the minimally invasive spine surgeon.

Enhancement of rotator cuff tendon–bone healing with injectable periosteum progenitor cells-BMP-2 hydrogel in vivo

The fixation and incorporation of ruptured rotator cuff tendon to bone is a major concern in rotator cuff repair surgery. Rotator cuff repair usually fails at the tendon-bone interface, especially in case of large or massive tears. To enhance tendon-bone healing, an injectable hydrogel made with periosteal progenitor cells(PPCs) and poly (ethylene glycol) diacrylate (PEGDA) tethered with bone morphogenic protein-2(BMP-2) was developed to encourage extracellular matrix synthesis for tendon-to-bone healing in rotator cuff repair. The infraspinatus tendon was cut from the greater tuberosity and repaired through a transosseous tunnel with the injectable progenitor cell-BMP-2 hydrogel applied between the tendon-bone interface. The injectable hydrogel was prepared from 10% poly (ethylene glycol) diacrylate (PEGDA) containing 0.05% of the photoinitiator. BMP-2 tethered with poly(ethylene glycol) (PEG) was blended to the hydrogel. Rabbit periosteal progenitor cells (PPCs) isolated from periosteum were mixed with hydrogel and injected on the tendon-bone interface. Ultraviolet radiation (365nm) was applied for 60s to photopolymerize the injection and solidify the hydrogel. The rabbits were killed at 4 and 8weeks. The morphological characteristics of the healing tendon-to-bone interface were evaluated by histological and immunohistochemical methods. The biomechanical test was done to determine healing attachment strength. At both the 4- and 8-week killing, histological analysis of the tendon-bone interface showed an increasing fibrocartilage and bone layer formed in the tendon-bone interface in PEGDA group. At 4weeks, fibrocartilage-like tissue was observed in a focal area. At 8weeks, further matrix deposition occurred with fibrocartilage formation in the tendon-bone junction, and bone formation appeared near host bone. Immunohistochemistry revealed the presence of aggrecan and type II collagen. Biomechanical testing revealed a higher maximum pull-out load at all time points with a statistically significant difference at 4 and 8weeks postoperatively. PEGDA hydrogel was approved as an adequate matrix for the encapsulation of cells and signal factor, and as an effective local delivery method to the tendon-bone interface through injection and photopolymerization. The PPCs-BMP2-hydrogel provides a powerful inductive ability between the tendon and the bone and enhances tendon-bone healing through the neoformation of fibrocartilage.

Outcomes of arthroscopic rotator cuff repairs in obese patients

Rotator cuff tears are common orthopedic injuries and their arthroscopic treatment can be technically challenging. This study evaluated the outcomes of arthroscopic rotator cuff repairs in obese patients. We hypothesized that there would be a direct correlation between worse outcomes of arthroscopic rotator cuff repairs and increasing body mass index (BMI). A retrospective review of patients undergoing arthroscopic rotator cuff repair by one orthopedic surgeon between 2005 and 2008 was performed. The study included 149 rotator cuff repairs. Recorded data included age, sex, BMI, size of rotator cuff tear on magnetic resonance imaging and intraoperatively, number of anchors used for repair, functional outcomes (American Shoulder and Elbow Surgeons and University of Pennsylvania scores), surgery time, total time for anesthesia, positioning, and hospital stay. Tears were classified by size. Strict inclusion and exclusion criteria were used. Surgical procedures were performed with general anesthesia, interscalene block, beach chair positioning, and a standardized operative technique. Patients followed a standard postoperative rehabilitation protocol. Mean patient age was 66 years. Mean follow-up was 16.3 months. Tears were classified as high grade partial (12%), small (23%), medium (29%), large (22%), and massive (14%). Patients were classified as normal weight (38%), overweight (23%), obese (20%), and morbidly obese (19%). A statistically significant correlation was found between obesity and worse functional outcomes, longer operative times, and longer length of hospital stay. This study reports new data concerning the association of BMI and early clinical outcome after arthroscopic rotator cuff repair surgery. Even though the obese group had greater limitations and lower rates of satisfaction at final follow-up than their non-obese counterparts, they still reported significant improvements from the surgery. Obesity has a negative impact on the operative time of arthroscopic rotator cuff repairs, length of hospitalization, and functional outcomes.

Osteolysis of the inferior surface of the acromion caused by knots of the suture thread after rotator cuff repair surgery: Knot impingement after rotator cuff repair

Osteolysis of the inferior surface of the acromion caused by knots of the suture thread after rotator cuff repair surgery: Knot impingement after rotator cuff repair

Arthroscopic rotator cuff repair: Clinical outcome of 606 patients

During the last decade arthroscopic repair has evolved to become common practice in the surgical treatment of symptomatic rotator cuff tendon tears. This paper reports the results of a consecutive series of patients who underwent arthroscopic rotator cuff repair surgery. All patients were independently assessed pre and post operatively utilizing the UCLA scoring system. All procedures were performed by a single surgeon, with a minimum of one year follow-up. Operative details were noted, including patient age, tear size, type of repair performed and concomitant procedures performed. Overall, 87% of patients had a good-excellent result. The results were found to be independent of tear size, tear configuration and concomitant procedures performed. This prospective study is one of the largest series of arthroscopic rotator cuff repairs reported. According to our results, 87% of patients who underwent arthroscopic rotator cuff repair have maintained good clinical outcomes up to 8 years after surgery.

Relationship between self-reported shoulder function/quality of life, body mass index, and other contributing factors in patients awaiting rotator cuff repair surgery

We hypothesized that body mass index (BMI) would be negatively associated with self-reported shoulder function/pain. A second objective was to investigate the significance of other potential contributing factors: age, sex, smoking status, tear size, and workers' compensation (WC) involvement. In this retrospective cohort study, consecutive patients who underwent arthroscopic rotator cuff repair surgery between 2002 and 2007 were reviewed. Preoperative American Shoulder and Elbow Society (ASES) and Simple Shoulder Test (SST) scores were compared with regard to age, sex, height, weight, smoking status, WC status, and rotator cuff tear size. Fifty-four patients were enrolled in this study. At a level of significance of P < .05, BMI showed no correlation with preoperative SST or ASES scores. WC status was negatively correlated with ASES scores. Female sex, WC status, and smoking were each negatively correlated with SST scores. The regression model predictive of preoperative SST scores included sex, WC status, and smoking status. WC status was predictive of ASES scores. To our knowledge, this is the first study to examine BMI as a contributing factor in the magnitude of pain and level of function in patients with chronic rotator cuff tears. Our data suggest that there is no impact of BMI on function/pain. The inter-relationships between factors such as BMI, sex, age, and others are complex, and further study is needed to fully establish that there is no effect. Our hypothesis that BMI is negatively related to magnitude of pain/level of function was not supported. Factors found to be related were sex, WC involvement, and smoking.

The effectiveness of continuous passive motion on range of motion, pain and muscle strength following rotator cuff repair: a systematic review

Objective: To systematically review the evidence on the effect of continuous passive motion, combined with usual physiotherapy management, on increasing shoulder joint range of motion and muscle strength, and reducing shoulder pain in adults following rotator cuff repair, compared with standard physiotherapy. Data sources: A comprehensive search in available bibliographic electronic databases was undertaken to locate eligible studies. Reference tracing was also used to locate studies. Review methods: Randomized controlled trials reporting on the effect of continuous passive motion on increasing shoulder joint range of motion and muscle strength and reducing shoulder pain in adults following rotator cuff repair were included in the review. The PEDro scale was used to determine the methodological quality of the studies. Data were summarized in a narrative form because of their heterogeneity. Results: Four randomized controlled trials were eligible for this review. One Japanese article was excluded as the text was unavailable in English. The methodological quality of the included studies averaged 7.67. Continuous passive motion was found to improve shoulder range of motion in two studies. One study found a decrease in pain in the intervention group and one study found that continuous passive motion improves muscle strength. Conclusion: Continuous passive motion is safe to use with physiotherapy treatment following rotator cuff repair surgery. It may help to prevent secondary complications post operatively.

Delivered growth factor therapy to improve healing after rotator cuff repair

BackgroundDegenerative rotator cuff tears are a significant cause of shoulder pain in the aging population. Rotator cuff repair surgery may be more successful when growth factors are delivered to the repair site. This study was designed to determine the cellular processes involved in normal bone-to-tendon healing and the current approaches used for biologic augmentation of rotator cuff repair.MethodsThis review focuses on animal studies of rotator cuff repair and early human trials.ResultsRegular bone-to-tendon healing forms a fibrous junction between tendon and bone that is markedly different from the original bone-to-tendon junction. Tendon augmentation with cellular components serves as scaffolding for endogenous fibroblastic cells and a possible source of growth factors and fibroblastic cells. Extracellular matrices provide a scaffold for incoming fibroblastic cells. However, research in extracellular matrices is not conclusive due to intermanufacturer variation and the lack of human subject research. Growth factors and platelet-rich plasma are established in other fields of research and show promise, but have not yet been rigorously tested in rotator cuff repair augmentation.ConclusionsRotator cuff repair can benefit from biologic augmentation. However, research in this field is still young and has not yet demonstrated that the benefits in healing rates are significant enough to merit regular clinical use. Randomized controlled trials will elucidate the use of biologic augmentation in rotator cuff repairs.

Bicipital groove morphology on MRI has no correlation to intra-articular biceps tendon pathology

Multiple authors have debated the contribution of intertubercular groove morphology to biceps tendon pathology. It has been proposed that the shallow groove, combined with the supertubercular ridge of Meyer, predisposes patients to bicipital disease. In this study we hypothesized that there would be a correlation between bicipital groove morphology and the intraoperative finding of biceps pathology. Seventy-five consecutive patients (average age of 63) undergoing arthroscopic rotator cuff repair surgery had their biceps tendons and intertubercular groove morphologies prospectively evaluated on closed MRI T1 axial cut images. The opening angle and medial wall angle of the bicipital groove was measured for each patient. At the time of surgery, the biceps tendon was classified as normal, inflamed, partially ruptured, or ruptured and the findings correlated to the bicipital groove measurements. The average opening angle was 81 degrees for normal biceps tendons and 77 degrees for torn biceps tendons. The average medial wall angle was 47 degrees for normal biceps tendons and 49 degrees for torn biceps tendons. Using Chi-square analysis, we found no statistically significant correlation between the bicipital groove average opening angle and medial wall angle on MRI and intraoperative biceps tendon pathology. This study does not support any correlation between intraarticular biceps tendon pathology and bicipital groove morphology.

The effect of medical comorbidity on self-reported shoulder-specific health related quality of life in patients with shoulder disease

The purpose of this study was to investigate further the effect of medical comorbidity on a patient reported shoulder specific health related quality of life (HRQoL) measure. We investigated which types of comorbidities have a detrimental effect upon shoulder specific HRQoL. We hypothesized that general medical comorbidity would not negatively affect shoulder specific HRQoL questionnaires, but that comorbidities specific to the chest region would, when properly controlling for other patient factors. A cohort of 173 consecutive patients who underwent shoulder surgery for osteoarthritis and/or rotator cuff repair was extracted from a clinical outcomes database. Their health related quality of life (HRQoL) was evaluated with the University of Pennsylvania (PENN) shoulder score and the Short Form-36 (SF-36). Nonadjusted and multivariate risk-adjusted models were built to investigate the effect of medial comorbidity on shoulder specific HRQoL and were tested using linear modeling. Nonadjusted models showed patients with more total comorbidities (P=.01) and more chest-related comorbidities (P=.006) had lower PENN scores. But, when risk adjusting for other patient factors, the PENN scores decreased with an increase in the number of chest comorbidities (P=.008), but not the number of total comorbidites (P=.391) or other (nonchest) comorbidities (P=.163). Shoulder specific HRQoL measures are joint specific, but they are influenced by disease or conditions that affect the chest region. This may be important in understanding why patients with certain comorbid diseases report worse shoulder pain and function and may respond differently to treatment over time.

Arthroscopic rotator cuff repair: clinical outcome of 607 patients

The purpose of this study was to evaluate the clinical results of rotator cuff tendon tears treated by arthroscopic repair with suture anchors. This prospective study included a cohort of 607 consecutive patients who underwent arthroscopic rotator cuff repair surgery. Most patients had a single-row type of repair using metal anchors. All patients were independently assessed pre- and post-operatively utilizing the UCLA (University of California at Los Angeles) scoring system with a minimum of 1 year follow-up. Demographic and operative details were noted; including the patient age, workers compensation status, tear size, type of repair performed, and concomitant procedures. The median UCLA score improved from 13 (0-28) to 35 (8-35) with a median follow-up time of 46 months (12-105), P < 0.001. The majority of the patients (529) achieved good to excellent results. The results were found to be independent of age, workers compensation status, tear size, type of repair performed and concomitant procedures. In conclusion, arthroscopic rotator cuff repair, using metal anchors with dual sutures, in a single row, utilizing margin convergence sutures and performing concomitant procedures when necessary, gave satisfactory results in 87% of patients.

Rotator cuff repair with periosteum for enhancing tendon–bone healing: a biomechanical and histological study in rabbits

During rotator cuff repair surgery, fixation and incorporation of ruptured rotator cuff tendon into the bone is a major concern. The repair usually fails at the tendon-bone interface, especially in cases where the tear is massive. The periosteum contains multipotent stem cells that have the potential to differentiate into osteogenic and chondrogenic tissues, which may restore the original structure at the tendon-bone interface, fibrocartilage. In this study, we investigated the effect of periosteum on the healing of the infraspinatus tendon and bone using a clinically relevant rabbit model of rotator cuff tear. We used 36 skeletally mature New Zealand white rabbits in the study. The infraspinatus tendon at right limb was detached from greater tuberosity, and a periosteal flap taken from the proximal tibia was sutured onto the torn end of tendon. The contralateral limb, which was used as a control, received the same treatment without a periosteum. The rabbits were sacrificed at 4, 8, and 12 weeks, and the tendon-bone interface was put to histological exam and the biomechanical testing to assess strength of tendon-bone interface. Histological analysis of the tendon-bone interface revealed that the periosteum formed a fibrous layer over the interface between tendon and bone. At 4 weeks, fibrotic tissue showed progressive integration over the interface between cuff tendon and bone. At 8 weeks, progressive formation of fibrovascular tissue and fibrocartilage was observed between tendon and bone. At 12 weeks, extensive formation of fibrocartilage and bone was noted in the interface. The significant increase of failure load with time indicated a progressive increase in the tendon-bone incorporation strength. At 4 weeks after operation, the attachment strength of the limbs with the periosteum treated was higher than that of the control limbs; however, this difference was not statistically significant. At 8 and 12 weeks, a statistically significant increase was noted in the attachment strength of the limb treated with the periosteum. Most specimens failed at the tendon-bone interface (18/20). In the treatment of a torn rotator cuff in rabbit model, improved healing process with greater attachment strength could be achieved by suturing the periosteum between the end of tendon and the bone trough. Histological examination revealed that the cambium layer of the periosteum could serve as a potent interface layer and become progressively mature and organized during the healing process, resulting in fibrocartilage formation and the subsequent integration of the disrupted tendon into the bone. Biomechanical testing revealed a progressive increase in the attachment strength with time indicating the progressive tendon-bone incorporation. When performing rotator cuff repair in a large or massive tear, a periosteal flap can be sutured onto the torn end of tendon to enhance tendon-bone healing.

A new nerve block procedure for the suprascapular nerve based on a cadaveric study

Shoulder pain after rotator cuff repair surgery is sometimes very severe. Suprascapular nerve block (SSNB) is a method used to relieve this shoulder pain, but is not always completely effective. The purpose of this study is to develop the new effective suprascapular nerve block procedure. To obtain an effective SSNB, we investigated an anatomic lesion of the sensory branches of the SSN in 8 cadavers and developed a new procedure. We evaluated its effectiveness by recording visual analog scale (VAS) scores in 8 patients experiencing severe pain after rotator cuff repair surgery before SSNB and for up to 24 hours postoperatively. All cadaver shoulders had 2 or 3 sensory branches that just passed the scapular notch. The branches originated from the SSN, pursued the base of the coracoid process, perforated the supraspinatus muscle, and extended toward the subacromial bursa. The average VAS score of the 8 patients postoperatively was 5.4 +/- 2.7 before SSNB and improved to 2.8 +/- 1.6 immediately after SSNB, to 1.2 +/- 0.6 at 1 hour, and to 0.8 +/- 0.8 at 4 hours. Effective pain control was achieved, and SSNB presented no complications. Our SSNB method is safe and effective for pain control in patients after open cuff repair. We expect it will be a useful management tool for pain relief after rotator cuff repair in the future. Basic science study.

Open, Mini-open, and All-Arthroscopic Rotator Cuff Repair Surgery: Indications and Implications for Rehabilitation

Rotator cuff tears lead to debilitating shoulder dysfunction and impairment. The goal of rotator cuff repair is to eliminate pain and improve function with increased shoulder strength and range of motion. The clinical outcomes of the surgical methods of rotator cuff repair (open, mini-open, and all-arthroscopic cuff repair) vary, as each method provides an array of advantages and disadvantages. Although the open surgical technique has long been considered the gold standard of rotator cuff repair, surgeons are becoming more adept at decreasing patient morbidity through decreased surgical trauma from an all-arthroscopic approach. In addition to a surgery-specific rotator cuff rehabilitation program, effective communication, and coordination of care by the physical therapist and surgeon are essential in optimal patient education and outcomes. In the ideal situation, a very well-educated therapist who has great communication with the treating surgeon can mobilize the shoulder early, re-establish scapulothoracic function safely and minimize the risk of stiffness and retear, while facilitating return to function. Treatment options can be individualized according to patient age, size and chronicity of tear, surgical approach, and fixation method. We recommend that patients who have undergone an all-arthroscopic rotator cuff repair undergo an accelerated postoperative rehabilitation program. A rational approach to therapy involves early, safe motion to allow optimal tendon healing, yet maintenance of joint mobility with minimal stress. As the field of orthopedics and, particularly, rotator cuff repair continues to develop with new technologies, the patient, physical therapist, and doctor need to work together to ensure optimal outcomes and patient satisfaction. Therapy, Level 5.

The Effect of Neuromuscular Electrical Stimulation of the Infraspinatus on Shoulder External Rotation Force Production after Rotator Cuff Repair Surgery

Background Muscle weakness, particularly of shoulder external rotation, is common after rotator cuff repair surgery. Neuromuscular electrical stimulation has been shown to be an effective adjunct in the enhancement of muscle recruitment. Hypothesis Shoulder external rotation peak force can be enhanced by neuromuscular electrical stimulation after rotator cuff repair surgery. Study Design Controlled laboratory study. Methods Thirty-nine patients (20 men, 19 women) who had undergone rotator cuff repair surgery were tested a mean of 10.5 days after surgery. Testing consisted of placing patients supine with the shoulder in 45° of abduction, neutral rotation, and 15° of horizontal adduction. Neuromuscular electrical stimulation was applied to the infraspinatus muscle belly and inferior to the spine of the scapula. Placement was confirmed by palpating the muscle during a resisted isometric contraction of the external rotators. Patients performed 3 isometric shoulder external rotation contractions with and without neuromuscular electrical stimulation, each with a 5-second hold against a handheld dynamometer. Neuromuscular electrical stimulation was applied at maximal intensity within comfort at 50 pulses per second, symmetrical waveform, and a 1-second ramp time. The 3 trials under each condition were recorded, and an average was taken. The order of testing was randomized for each patient tested. A paired samples t test was used to determine significant differences between conditions (P < .05). Each group was also divided based on age, rotator cuff tear size, number of days postoperative, and neuromuscular electrical stimulation intensity. Analysis of variance Models were used to determine the influence of these variables on external rotation force production (P < .05). Results Peak force production was significantly greater (P < .001) when tested with neuromuscular electrical stimulation (3.75 kg) as opposed to without neuromuscular electrical stimulation (3.08 kg) for all groups tested. There was no significant difference based on the size of the tear, age of the patient, number of days after surgery, or level of neuromuscular electrical stimulation intensity. Conclusion Peak shoulder external rotation force was significantly increased by 22% when tested with neuromuscular electrical stimulation after rotator cuff repair surgery. Neuromuscular electrical stimulation significantly increased force production regardless of the age of the patient, size of the tear, intensity of the current, or the number of days postoperative. Clinical Relevance Neuromuscular electrical stimulation may be used concomitantly with exercises to enhance the amount of force production and potentially minimize the inhibition of the rotator cuff after repair surgery.

Tendon bone healing can be enhanced by demineralized bone matrix: A functional and histological study

Rotator cuff repair surgery has high failure rates, with tendon reattachment to bone remaining a challenging clinical problem. Increasing the integrity of the healing tendon-bone interface has been attempted by adopting a number of different augmentation strategies. Because of chondrogenic and osteogenic properties we hypothesise that demineralized bone matrix (DBM) augmentation of a healing tendon-bone interface will result in improved function, and a morphology that more closely resembles that of a normal enthesis, compared with nonaugmented controls in an ovine patellar tendon model. The right patellar tendon was detached from its insertion and reattached to an osteotomized bone bed using suture anchors. Two groups were analyzed, the control group (without augmentation) and the DBM group (DBM interposed between the tendon and bone). Animals were sacrificed at 12 weeks. Force plate, mechanical, and histomorphometric analyses were performed. Tendon repairs failed at a rate of 33 and 0% for the control and DBM groups, respectively. DBM augmentation resulted in significantly improved functional weight bearing and increased amounts of fibrocartilage and mineralized fibrocartilage. This study shows that DBM enhances tendon-bone healing and may reduce the high failure rates associated with rotator cuff repair clinically.

An integer programming model for optimizing shoulder rehabilitation.

Strength restoration is one goal of shoulder rehabilitation following rotator cuff repair surgery. However, the time spent in a physical rehabilitation setting is limited. The objective of this study was to develop a novel mathematical formulation for determining the optimal shoulder rehabilitation exercise protocol to restore normal shoulder strength given a time-constrained rehabilitation session. Strength gain was modeled using a linear dose-response function and biomechanical parameters of the shoulder musculature. Two different objective functions were tested: (1) one based on a least squares support vector machine using healthy and pathologic shoulder strengths (normative objective function), and (2) one which seeks to match the strength of the contralateral shoulder (contralateral objective function). The normative objective function was subject-independent and the optimal protocol consisted of four sets each of adduction and external rotation. The contralateral objective function was subject-specific and the typical optimal protocol consisted of various set combinations of abduction and internal and external rotation. These results are only partially consistent with current practice. Improvement of the current model is dependent on a better understanding of strength training adaptation and shoulder rehabilitation.

Biological Augmentation of Rotator Cuff Tendon Repair

A histologically normal insertion site does not regenerate following rotator cuff tendon-to-bone repair, which is likely due to abnormal or insufficient gene expression and/or cell differentiation at the repair site. Techniques to manipulate the biologic events following tendon repair may improve healing. We used a sheep infraspinatus repair model to evaluate the effect of osteoinductive growth factors and BMP-12 on tendon-to-bone healing. Magnetic resonance imaging and histology showed increased formation of new bone and fibrocartilage at the healing tendon attachment site in the treated animals, and biomechanical testing showed improved load-to-failure. Other techniques with potential to augment repair site biology include use of platelets isolated from autologous blood to deliver growth factors to a tendon repair site. Modalities that improve local vascularity, such as pulsed ultrasound, have the potential to augment rotator cuff healing. Important information about the biology of tendon healing can also be gained from studies of substances that inhibit healing, such as nicotine and antiinflammatory medications. Future approaches may include the use of stem cells and transcription factors to induce formation of the native tendon-bone insertion site after rotator cuff repair surgery.