Kenneth A. Egol

Biomechanics of locked plates and screws

Objective: To review the biomechanical principles that guide fracture fixation with plates and screws; specifically to compare and contrast the function and roles of conventional unlocked plates to locked plates in fracture fixation. We review basic plate and screw function, discuss the design rationale for the new implants, and examine the biomechanical evidence that supports the use of such implants. Data Sources: Systematic review of the per reviewed English language orthopaedic literature listed on PubMed (National Library of Medicine online service). Study Selection: Papers selected for this review were drawn from peer review orthopaedic journals. All selected papers specifically discussed plate and screw biomechanics with regard to fracture fixation. PubMed search terms were: plates and screws, biomechanics, locked plates, PC-Fix, LISS, LCP, MIPO, and fracture fixation. Data Synthesis: The following topics are discussed: plate and screw function—neutralization plates and buttress plates, bridge plates; fracture stability—specifically how this effects gap strain and fracture union, conventional plate biomechanics, and locking plate biomechanics. Conclusions: Locked plates and conventional plates rely on completely different mechanical principles to provide fracture fixation and in so doing they provide different biological environments for healing. Locked plates may increasingly be indicated for indirect fracture reduction, diaphyseal/metaphyseal fractures in osteoporotic bone, bridging severely comminuted fractures, and the plating of fractures where anatomical constraints prevent plating on the tension side of the bone. Conventional plates may continue to be the fixation method of choice for periarticular fractures which demand perfect anatomical reduction and to certain types of nonunions which require increased stability for union.

Staged management of high-energy proximal tibia fractures (OTA types 41): the results of a prospective, standardized protocol.

Objectives: This study evaluated the use of a staged protocol involving temporary spanning external fixation and delayed formal definitive fixation in the management of high-energy proximal tibia fractures (OTA types 41) with regard to soft-tissue management, development of complications, and functional outcomes. Setting: Two level-one trauma centers and a tertiary care orthopaedic center. Patients: Fifty-three patients with 57 high-energy tibial plateau fractures. Methods: The authors instituted a protocol of immediate placement of knee spanning external fixation with management of soft-tissue injuries for all high-energy proximal tibia fractures. Between August 1999 and May 2002, 62 consecutive patients with 67 high-energy proximal tibia fractures (OTA types 41A, B, C) underwent temporary knee spanning external fixation on the day of admission. Nine patients with 10 fractures who transferred care after initial stabilization or sustained an extraarticular fracture were excluded. The remaining 53 patients with 57 fractures underwent repair of articular fractures and meta-diaphyseal fracture repair with plates and screw constructs or conversion to a ring fixator. These patients had a mean age of 47 years (standard deviation (SD), 14). Of these 53 patients, 42 (79%) were men and 11 (21%) were women. Characteristics of the 57 fractures were: 42 Schatzker VI (74%), 12 Schatzker V (21%), 2 Schatzker IV (4%), and 1 Schatzker II (2%). There were 41 closed fractures and 16 open fractures. (One patient had bilateral fractures with 1 extremity open and 1 closed). Orthopaedic evaluation at latest follow-up included a clinical and radiographic examination and functional outcome measurement with the Western Ontario McMaster functional knee score (WOMAC). Eight patients with 8 fractures were lost to follow-up. This left 45 patients with 49 fractures with a mean follow-up of 15.7 (SD, 5.7; range, 8-40) months. Results: Complications included 3 (5%) deep wound infections, 2 (4%) nonunions, and 2 patients (4%) with significant knee stiffness (<90°). Nine patients (16%) underwent additional surgery after definitive skeletal stabilization related to their injury. Range of knee motion at final follow-up was 1° (SD, 4) to 106° (SD, 15). The mean WOMAC was 91 (SD, 55). Poor results did not correlate with demographic or injury characteristics. Discussion: We had a relatively low rate of wound infection in these complex injuries (5% overall). There was only 1 wound problem in our subset of patients with closed fractures and 2 infections in those with open fractures. One downside of this technique may be residual knee stiffness. The benefits of temporizing spanning external fixation include osseous stabilization, access to soft tissues, and prevention of further articular damage. Our relatively low rates of complications in patients who sustain high-energy proximal tibia fractures and the access this technique affords in open fractures and those with compartment syndrome lead us to recommend this technique in all high-energy intra-articular and extra-articular fractures of the proximal tibia. Clinical Relevance: This study supports the practice of delayed internal fixation until the soft-tissue envelope allows for definitive fixation.

Early complications in proximal humerus fractures (OTA Types 11) treated with locked plates.

Purpose: To examine our incidence of early complications that occur using the Proximal Humeral Internal Locking System (PHILOS) and to determine the contributing factors. Setting: Academic medical center. Patients: Fifty-one consecutive patients treated with a proximal humerus locking plate. Outcome: Development of an intraoperative, acute postoperative, or delayed postoperative complication. Methods: A retrospective analysis was undertaken of a consecutive series of proximal humerus fractures treated with a locking plate between February 2003 and January 2006 at our institution. Fifty-one fractures or fracture nonunions were identified in 18 male and 33 female patients with an average age of 61. All acute injuries were treated with a similar protocol of open reduction internal fixation with the PHILOS plate followed by early range of shoulder motion. Nonunions were treated in a similar manner with the addition of iliac crest bone graft placement. Patients were objectively assessed on their outcome by physical as well as radiological examination. All complications were recorded. Statistical analyses were performed to determine if patient age, fracture type, or number of screws placed in the humeral head contributed to complications. Results: Fifty-one patients were available for minimum 6-month follow-up (mean, 16 months; range, 6 to 45 months). Radiographically, 92% of the cases united at 3 months after surgery, and 2 fractures had signs of osteonecrosis at latest follow-up. Sixteen complications were seen in 12 patients (24%). Eight shoulders in eight patients (16%) had screws that penetrated the humeral head. Two patients developed osteonecrosis at latest follow-up. One acute fracture and one nonunion failed to unite after index surgery. Significant heterotopic bone developed in 1 patient. Early implant failure occurred in 2 patients; one was revised to a longer plate, and one underwent resection arthroplasty. There was one acute postoperative infection. Conclusion: The major complication reported in this study was screw penetration, suggesting that exceptional vigilance must be taken in estimating the appropriate number and length of screws used to prevent articular penetration; although the device provides exceptional fixation stability, its indication must be scrutinized for each individual patient, taking the extent of trauma/fracture and age into consideration and carefully weighing it against other forms of treatment.

Predictors of short-term functional outcome following ankle fracture surgery.

BACKGROUND Ankle fractures are among the most common injuries treated by orthopaedic surgeons. However, very few investigators have examined the functional recovery following ankle fracture surgery and, to our knowledge, none have analyzed factors that may predict functional recovery. In this study, we evaluated predictors of short-term functional outcome following surgical stabilization of ankle fractures. METHODS Over three years, 232 patients who sustained a fracture of the ankle and were treated surgically were followed prospectively, for a minimum of one year. Trained interviewers recorded baseline characteristics, including patient demographics, medical comorbidities, and functional status according to the Short Musculoskeletal Function Assessment (SMFA). Laboratory findings, the American Society of Anesthesiologists (ASA) class, and operative findings were recorded from the chart during hospitalization. Follow-up information included the occurrence of complications or additional surgery, weight-bearing status, functional status according to the SMFA, and the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score. The data were analyzed to determine predictors of functional recovery at three months, six months, and one year postoperatively. RESULTS Complete follow-up data were available for 198 patients (85%). At one year, 174 (88%) of the patients had either no or mild ankle pain and 178 (90%) had either no limitations or limitations only in recreational activities. According to the AOFAS ankle-hindfoot score, 178 (90%) of the patients had > or = 90% functional recovery. A patient age of less than forty years was a predictor of recovery, as measured with the SMFA subscores, at six months after the ankle fracture. At one year, however, age was no longer a predictor of recovery. Patients who were younger than forty were more likely to recover > or = 90% of function (p = 0.004), and men were more likely than women to recover function (p = 0.02). ASA Class 1 or 2 (p = 0.03) and an absence of diabetes (p = 0.02) were also predictors of better functional recovery at one year. SMFA subscores were below average at baseline, indicating a healthy population. At three and six months postoperatively, all SMFA subscores were significantly higher than the baseline subscores (p < 0.001); however, at one year, the SMFA subscores were almost back to the baseline, normal level. CONCLUSIONS One year after ankle fracture surgery, patients are generally doing well, with most experiencing little or mild pain and few restrictions in functional activities. They have a significant improvement in function compared with six months after the surgery. Younger age, male sex, absence of diabetes, and a lower ASA class are predictive of functional recovery at one year following ankle fracture surgery. It is important to counsel patients and their families regarding the expected functional recovery after an ankle injury.

The relationship between admission hemoglobin level and outcome after hip fracture

Objective: To determine the effect of admission hemoglobin level on patient outcome after hip fracture. Study Design: Prospective, consecutive. Patients: From July 1991 to June 1997, 395 communitydwelling patients sixty‐five years of age or older who had sustained an operatively treated femoral neck or intertrochanteric fracture were prospectively followed up. Main Outcome Measurements: Postoperative complications, in‐hospital mortality rate, hospital length of stay, hospital discharge status, place of residence at one year, and mortality and recovery of ambulatory ability and activities of daily living status at three, six, and twelve months. Results: Women with admission hemoglobin levels below 12.0 grams per deciliter and men with admission hemoglobin levels below 13.0 grams per deciliter were classified as anemic. One hundred eighty patients (45.6 percent) were considered anemic on admission. Patients who were anemic were more likely to have an American Society of Anesthesiologists rating of III or IV and have sustained an intertrochanteric fracture. Hospital length of stay and mortality rate at six and twelve months were significantly higher for patients who were anemic on admission. There were no differences in the incidence of postoperative complications, hospital discharge status, place of residence at one year, in‐hospital mortality rate, and three‐month mortality rate between patients who were and were not anemic on admission. In addition, there were no differences in the recovery of ambulatory ability and of basic and instrumental activities of daily living status at three, six, and twelve months between the two patient groups. Conclusions: Patients at risk for poor outcomes after hip fracture can be identified by assessing hemoglobin levels at hospital admission.

Gender differences in patients with hip fracture: A greater risk of morbidity and mortality in Men

Objective: To determine gender-specific differences in prefracture status and postoperative outcome in elderly hip fracture patients who were ambulatory, community-dwelling, and cognitively intact prior to fracture. Design: Retrospective analysis of prospectively collected data. Setting: Urban orthopedic referral hospital. Patients: A total of 983 consecutive patients (206 males and 777 females) who sustained a nonpathologic hip fracture were followed for a minimum of 12 months. Intervention: Operative treatment of a proximal femur fracture. Main Outcome Measurements: Postoperative medical complications, place of discharge, 1-year mortality, and postoperative recovery of ambulation, basic activities of daily living, and instrumental activities of daily living. Results: Men were more likely to be married or living with someone else, and they were more dependent in instrumental activities of daily living than women prior to hip fracture. Furthermore, men were sicker as evidenced by a higher American Society of Anesthesiologists rating of preoperative risk. Postoperatively, men were more likely to sustain a medical complication and had a higher mortality at 1 year compared to women. There were no statistically significant gender differences in patient age, fracture type, prefracture level of help, ambulation, or dependence in basic activities of daily living, place of discharge, and postoperative recovery of ambulation as well as basic and instrumental activities of daily living. Conclusions: Male gender was a risk factor for sustaining a postoperative complication as well as a higher mortality at 1 year post hip fracture.

Stress Fractures of the Femoral Neck

Stress fractures of the femoral neck are uncommon injuries. In general these injuries are seen in two distinct populations: (1) young, healthy, active individuals such as recreational runners, endurance athletes, or military recruits; and (2) the elderly who have osteoporosis. Stress fractures can be classified as either fatigue or insufficiency fractures and result from untoward cyclic loading or impaired bone quality. The key to treatment is early diagnosis, which may require scintigraphy or magnetic resonance imaging. Nondisplaced compression type stress fractures can be treated nonoperatively with protected weight-bearing and frequent radiographic followup. Tension type stress fractures should be stabilized internally to prevent the adverse consequences of fracture displacement.

Bridging external fixation and supplementary Kirschner-wire fixation versus volar locked plating for unstable fractures of the distal radius: A RANDOMISED, PROSPECTIVE TRIAL

We performed a prospective, randomised trial to evaluate the outcome after surgery of displaced, unstable fractures of the distal radius. A total of 280 consecutive patients were enrolled in a prospective database and 88 identified who met the inclusion criteria for surgery. They were randomised to receive either bridging external fixation with supplementary Kirschner-wire fixation or volar-locked plating with screws. Both groups were similar in terms of age, gender, hand dominance, fracture pattern, socio-economic status and medical co-morbidities. Although the patients treated by volar plating had a statistically significant early improvement in the range of movement of the wrist, this advantage diminished with time and in absolute terms the difference in range of movement was clinically unimportant. Radiologically, there were no clinically significant differences in the reductions, although more patients with AO/OTA (Orthopaedic Trauma Association) type C fractures were allocated to the external fixation group. The function at one year was similar in the two groups. No clear advantage could be demonstrated with either treatment but fewer re-operations were required in the external fixation group.

The evolution of locked plates

Our purpose is to review the history of locked plates and the current recommendations for the use of those devices and to look toward future trends in the clinical application of locked plates. We will discuss (1) the impetus for the locked (fixed-angle) plate design, (2) current indications and design trends, (3) the latest clinical and biomechanical data, (4) shortcomings of locked (fixed-angle) plates, and (5) future applications and directions for locked (fixed-angle) plates. Since their initial introduction in the late nineteenth century and their subsequent popularization by Danis1-3 and the Arbeitsgemeinschaft fur Osteosynthesefragen (AO) group in the 1960s, conventional nonlocked plates have proven, over time, to successfully stabilize many types of fractures and osteotomy sites. The plate-screw-bone construct must resist physiological loads to allow fracture union by limiting fracture gap stress, provide sufficient stability to permit early limb motion, and not fail before fracture union occurs. Additionally, for optimal clinical results, disruption of the bone blood supply by the plate-screw-bone construct should be minimized. To accomplish this goal, there should be minimal operative dissection and periosteal contact to promote bone union4,5. Ideally, the plate-screw-bone construct will permit the restoration of the mechanical limb alignment and reestablish joint congruity to within <2 mm2,6,7. Finally, to be successful, plate fixation must provide reproducible results, must be simple to perform, and must have broad clinical applicability. Fixation with conventional compression plates, although for the most part successful, has its limitations. Figure 1 demonstrates one attempt to counter the limitations associated with the use of conventional nonlocked plates. To achieve fracture stability, the axial, torsional, and three-point bending forces must be neutralized (Fig. 2). With the use of conventional nonlocked plates, force friction between the plate and the bone counters …

Fixation of periprosthetic femoral shaft fractures associated with cemented femoral stems: a biomechanical comparison of locked plating and conventional cable plates.

To determine which of 2 techniques for the treatment of periprosthetic femoral shaft fractures is of greater stiffness. Design: A laboratory study using 8 pairs of matched, embalmed femurs. Methods: Femurs implanted with a cemented total hip prosthesis had a simulated periprosthetic femur fracture created distal to the implant. Fractures were fixed with a plate with locked screws or a plate with cables (Ogden construct). Fixation stability was compared in various loading modalities before and after cycling. Failure in torsional loading was then determined. The cement mantle was tested for crack propagation that may have occurred secondary to locked screw insertion and loading. Outcome Measurements: Fixation stiffness (the ratio of applied load to displacement at the fracture site), torsional strength, mode of failure for each system, and cement mantle evaluation for cracks after screw insertion. Results: Locked plating was stiffer than the Ogden construct in pre- and post-cyclic axial loading and torsion. There was no difference in lateral bending stability or torsional failure loads. Conclusions: Locked plating constructs were stiffer than the Ogden construct in axial loading and torsion. Although no differences in loads to failure during torsion were noted, locked plating constructs exhibited catastrophic failure not observed with the Ogden construct.