The Hand Surgery Service at Massachusetts General Hospital has treated a relatively large number of patients with ununited fractures of the humerus (7, 11, 15-18) . In treating these patients, we have learned how difficult it can be to obtain fixation that is stable enough to allow healing in the presence of poor bone quality. A number of specific techniques and implants have been developed to facilitate skeletal fixation of poor quality bone (15, 17).

Background

The Problem

Fractures are more common in the elderly, due to loss of bone mineral density and the normal hormonal changes associated with menopause (6) . Metaphyseal fractures, such as those of the proximal and distal humerus are often associated with osteoporosis. In addition, many older persons are undernourished (4). Others have diminished bone density from limited activity. Older patients with ununited fractures may exhibit many of these factors and also lose bone from disuse, because their ununited limb is often painful and unstable (6).

Fracture healing requires a good vascular supply, stability, and bone apposition (23). Nonunions occur when the blood supply is insufficient, when there is excess motion, or when there is soft tissue interposition or a bony gap.

When a fracture of the humerus that has been treated non-operatively fails to heal, it is usually due to excess motion. Often a false joint, or synovial psuedoarthrosis develops at the fracture site and all attempts at healing are arrested (23).

Failure of an operatively treated fracture to heal may be related to a number of factors including devascularization of fracture fragments as a result of the exposure and application of implants, distraction of fragments by an implant, loosening or breakage of inadequate implants with resultant inflammatory response, or infection. Synovial psuedoarthrosis can form in the presence of a loose implant. (Fig. 1) Loose implants can cause bone loss that hinders effective fixation. One example is the loose intramedullary implant that, through repetitive motion in the intramedullary canal, can dramatically thin the cortices of the bone (12) . (Fig. 1) Once the fracture site has been debrided of synovial tis-sues and avascular bone—particularly in the setting of prior infection or a loose implant—there may be a bony defect at the fracture site. Although the upper extremity tolerates shortening relatively well, in some cases the ability to shorten is limit-ed by a desire to limit the elevation of muscle and periosteum from the bone in order to preserve its vascular supply (14) . As a result, the surgeon is often faced with the need to obtain heal-ing across a bony gap.

Figure 1: An ununited fracture that fails to heal after intramedullary rod fixation can be challenging to treat effectively. Extraction of the rod can be difficult and may injure the shoulder; motion of the rod has led to substantial thinning of the cortices; and, in spite of the fixation, there is a synovial nonunion

To obtain healing, the surgeon must gain adequate fixation while preserving the vascular supply to the bone and surrounding soft tissue envelope. Any defects must be filled with autogenous cancellous bone graft. None of the currently available bone graft substitutes have been proven to be reliable for the treatment of ununited fractures.

The Need to Address the Problem

Achieving stable fixation in the presence of diminished bone quality, loose implants, and bony defects represents a substantial challenge (17, 19, 20) . In fact, some surgeons consider it risky to consider operative treatment in older patients with complex ununited fractures of the humerus. On the other hand, an unstable, ununited fracture can be extremely dis-abling and painful. The disability associated with an ununited fracture may be greater in an older person who is less capable of adapting to adversity.

We have measured the disability associated with an ununited fracture of the humeral diaphysis in an older patient using the Disabilities of the Arm, Shoulder, and Hand (DASH) instrument and the Enforced Social Dependency Scale (ESDS) (17) . The DASH instrument consists of 21 questions about difficulty performing specific activities, 5 questions about symptoms, and 4 general health status questions. A higher score indictates greater dysfunction. The DASH scores for patients with ununited fractures of the humerus averaged 77 points, with the poorest score being 94 out of 100 points. These poor pre-operative scores were improved to an average of 24 points after operative treatment (17) .

The Enforced Social Dependency Scale is an interview-based scale that was developed by nurses for the evaluation of patients who become dependent upon others for activities of daily living due to illness (1) . Although initially applied to med-ical illnesses such as heart failure and cancer, the ESDS is also appropriate in the evaluation of musculoskeletal problems. The scale has the ability to stratify among patients with very limited dependence upon others to those in a vegetative state. Pre-operatively, patients scored an average of 39 out of 100 points on a standardized scale. Scores improved to an average of 9 points after operative treatment, indicating substantial restoration of independent functioning (17) .

These outcome instruments helped to quantify the impact that an ununited fracture of the distal humerus can have on a patient’s quality of life and ability to function independently. The dramatic improvement in scores for patients with unstable ununited fractures demonstrates the importance of devel-oping reliable means to gain stable fixation of the osteoporotic skeleton.

Fixation Techniques

	Figure 2: Older patients with ununited fractures of the diaphyseal humerus often have very poor bone quality. One method for improving the security of fixation is to use long plates. It is possible to gain extensile exposure through a number of different approaches. When the plate spans nearly the entire bone, fractures at the ends of the plates are less likely.	Long Plates Longer plates are advantageous in a number of respects. The most obvious is that a longer plate provides stronger fixation. The larger the space between the screws closest to and furthest from the fracture site, the higher the resistance to bending loads (22) . An increased number of screws helps resist torsional loads, particularly if the screws are oriented in diverging directions(22) . Additional benefits of longer plates in osteopenic bone include a decrease in the impact of a single loose screw as well as support of a greater length of the bone by the implant so that fractures at the limit of the plate are less likely. (Fig. 2)

Plates in Orthogonal Planes The placement of 2 plates in orthogonal planes is another means of achieving increased biomechanical stability and strength of fixation.(Fig. 3) This has been successfully applied in the distal humerus where standard recommendations are for two plates in orthogonal planes (5) . We have also used 3 plates to fix ununited fractures of the distal humerus (where the articular fragments are often small and osteopenic), and frac-tures with small articular fragments (7) . In addition to a medial plate that cradles the medial epicondyle, two orthogonal plates are applied to the lateral column.		Figure 3: With newer plate designs and operative exposures, it is possible to use two plates in orthogonal planes without devascularizing the bone. This is often useful in the fixation of ununited fractures with poor quality bone. One example is this ununited fracture of the distal diaphysis.

The use of orthogonal plates in the treatment of diaphy-seal fractures was unsuccessful in earlier applications (21) . However, those earlier studies were performed when subpe-riosteal dissection and plates with a large surface area in contact with the bone were used. It is likely that these techniques disrupted the blood supply to the bone and limited the biological capacity of the bone to heal (13) . With newer exposures which limit the elevation of muscle from bone and leave the perios-teum in place, and modern low-contact implants, such as the limited contact dynamic compression plate (LC-DCP; Synthes, Ltd., Paoli, PA) (13) , the PC-Fix (Synthes, Ltd.; Paoli, PA), and the so-called wave plate (2, 3, 14, 16) , it may be possible to take advantage of the biomechanical advantages of orthogonal plates without compromising the biological aspects of bone healing.

Fixed-Angle Fixation Devices

Blade Plates Standard screws depend upon engagement of the screw threads with the bone-commonly referred to as “purchase”. Engagement of the threads within the bone secures a plate to the bone or two fragments together when an interfragmentary compression screw is used. If screw threads gain poor hold in the bone (in other words if a screw “strips”) it is no longer effective in stabilizing the bone. The screw can then toggle and back out and does not increase the compression or friction between the plate and bone or bone fragments. Blade plates provide a broad, fixed hold on the bone that does not rely upon engagement of threads to provide stability. (Fig. 4) Even if the blade does not tightly engage the surrounding bone, it will have to plow through the bone or back out to lose fixation entirely. The broad area of the blade is particularly useful for gaining fixation in metaphyseal bone. (Fig. 3, 5)

Figure 4: Blade plates offer a more secure fixation of osteopenic bone.

Schuhli Nuts

Nuts are occasionally applied to screws in an attempt to improve fixation. (Fig. 5B) The drawbacks of standard nuts include the need for an extensive, devascularizing exposure to apply the nut on the opposite cortex. In addition, the screw will still loosen and toggle, particularly with cyclic loading, if its threads do not engage the bone.

Figure 5: A: After two operative attempts to gain union, this proximal diaphyseal fracture of the humerus remains ununited.	B: After debridement of the synovial nonunion, fixation of the poor quality bone was achieved using a combination of a blade plate and screws rein-forced with Schuhli washers.	C: The fixation was stable enough to allow functional motion in the immediate post-operative period. Note that the patient’s staples have not yet been removed.

A new type of nut—the Schuhli nut 8-10 —has been developed as a means to enhance the fixation of osteopenic bone. The Schuhli nut is applied underneath a plate, between the plate and bone on the near cortex.(Fig. 6) It locks into the plate so that when a screw is fully threaded in to the plate it becomes a fixed-angle device. Even if the screw has limited engagement or purchase in the bone, it still provides stability just as the blade of a blade plate does. In addition, the nut has spikes that increase the friction between the plate and the bone. The nuts raise the plate off of the bone, thereby decreas-ing its contact area and making it a more limited contact implant.

Figure 6: The Schuhli washer lies directly under the plate on the near cortex as opposed to standard washers that are applied opposite the plate. After a screw is threaded through a Schuhli washer it is incorporated into the plate as a fixed-angle device. The washers have spikes to increase friction between the plate and bone and they also serve to limit plate-bone contact.

Results

We have used these principals, techniques, and implants in the treatment of ununited fractures of the humerus at various levels and for various types of fractures.

Ununited Fractures of the Distal Humerus

The senior author (JBJ) has treated over 40 patients with an ununited fracture of the distal humerus. A large percentage of these patients were women over 60 years of age. Many of them had synovial nonunions, and some had intra-articular nonunions. Older patients with ununited fractures of the distal humerus are treated with a combination of three plates( 7) : the medial plate wraps around the medial epicondyle, providing for an increased number of screws in the medial fragment with the most distal screw oriented orthogonal to the more proximal screws; the lateral column is secured with two orthogonal plates—one directly posterior and the other directly lateral on the lateral column. The elbow capsule is released through the fracture site, the fracture site is debrided to bleeding bone, and autogenous bone graft is applied (7, 11) . Post-operatively, patients are splinted in extension, and active, gravity-assisted elbow mobilization is initiated the day after surgery. Healing was achieved in each case with an average of 95 degrees of ulno-humeral motion ultimately obtained, in some cases after a secondary elbow capsular release.

Ununited Fractures of the Humeral Diaphysis

We recently published the results of the operative treatment of 22 older-aged patients with unstable ununited fractures of the humeral diaphysis (17) . Plate length averaged 76% of the length of the humerus. Modifications of standard plating technique included the use of a blade plate in 13 patients, Schuhli nuts in 6 patients, replacement of a loose 4.5 millimeter cortical screw with a 6.5 millimeter cancellous screw in 12 patients, augmentation of a loose 4.5 millimeter cortical screw with cement in 2 patients, and use of an allograft strut to enhance screw fixation in 2 patients. In addition, 5 patients had bony defects addressed with a second intramedullary plate in 2 patients, and a wave plate in 3 patients. Healing was achieved in all but two patients. The fixation remains stable in the two patients with persistent fracture lines, suggesting fibrous union. The functional improvements were dramatic both objectively and subjectively with 77% of patients achiev-ing good or excellent results and the improvements based on the outcome measures documented above (17) .

Ununited Fractures of the Proximal Humerus

In a combined series with Michael McKee, MD in Toronto, we have reviewed the treatment of 25 patients with ununited fractures of the proximal humerus using blade plate fixation (18) . About two-thirds of these patients were older than 60. Only two fractures failed to unite, but the fixation remained stable in each case. Again, marked functional improvements were recorded both subjectively and objectively.

Fractures of the Humerus Associated with a Bony Defect

In a combined series with Dr. Rene Marti in Amsterdam, Dr. Richard Sanders in Birmingham, and Dr. Jaime Quintero in Columbia, we have studied the results of treatment of 15 patients with ununited fractures of the humerus associated with a bony defect at the fracture site (16) . When a defect is present as a result of debridement of an originally open fracture, a subsequently infected one, a synovial nonunion, or loose implants with devascularized bone, we have used the so-called wave plate (2, 3, 14, 16) . Wave plate osteosynthesis consists of a plate contoured to stand away from the bone about _ to 1 centimeter at the fracture site. Bone graft is applied both beneath the plate and in the fracture site. The wave contour improves the access of the blood supply from the surrounding musculature to the underlying bone grafts. It also distributes bending stresses over a greater area of the plate, thus limiting the potential for fatigue failure under cyclic loading. Finally, itfacilitates restoration of a tension band function of the plate, since the lateral translation of the bending moment that results from the contour of the plate distributes compressive forces to the near cortex. Restoration of this cortex by incorporation of the bone grafts placed underneath the plate leads the plate to act as a tension band, thereby improving the mechanics of the plate-bone construct. All but one of the patients treated with wave plate osteosynthesis healed.

Conclusions

The operative treatment of ununited fractures of the humerus presents a formidable task as a result of the poor bone quality that is often encountered in this patient popula-tion. However, the extreme disability associated with a painful, unstable nonunion mandates that we address this challenge. A number of recent developments in the implants and techniques for the fixation of poor quality bone have proven useful in the treatment of our patients with ununited fractures of the humerus at all levels, including those with bony defects. We continue to address the need for stable fixation of poor quality bone both in the care of our patients, as well as in the biomechanics laboratory.