Comparison of innervated and noninnervated free flaps in oral reconstruction

Rehabilitation following surgery for reconstruction of a foot defect

Background

This report illustrates the use of pressure for scar management to aid in foot re-shaping following a surgical intervention to repair an arterio-venous (AV) malformation.

Methods

This report describes the rehabilitation of a 13-year-old girl after surgical reconstruction of a defect in her left foot following the removal of an AV malformation. Early surgical attempts to repair the problem resulted in complications that required the amputation of toes 2, 3, and 4, and the use of a split thickness skin graft to cover the plantar surface of the medial longitudinal arch on the left foot. Following surgery, the patient had an antalgic gait pattern with decreased weight bearing on the left. The graft obliterated the left medial longitudinal arch and the patient would only weight bear on the heel. The patient had decreased metatarsal joint mobility on the affected side and no movement in the remaining toes. Left talocrural joint active range-of-motion (AROM) was within normal limits and gross ankle muscle force production was assessed to have a grade of 3/5.

Results

Treatment included reshaping the left foot using a pressure garment and orthotic, followed by interventions to address range-of-motion and muscle force production deficiencies. All treatment objectives were achieved and all patient goals were achieved.

Conclusions

Pressure was effective in re-shaping the foot to promote normal gait mechanics.

Analysis of Determinants on Speech Function After Glossectomy

PURPOSE

To determine which of the following factors-type of reconstruction, size of tumor, and site of excision-may influence speech intelligibility after glossectomy.

MATERIALS AND METHODS

The speech intelligibilities of 27 tongue cancer patients who underwent glossectomy within the range of the hemitongue were investigated within 6 months after operation with a speech intelligibility test formed by 100 sensitive Chinese sounds. They were compared according to the following factors: type of reconstruction (forearm flap or adjacent flap); size of tumor (T1, T2, T3); and site of excision (anterior, middle, posterior, or hemi part).

RESULTS

There was no significant difference in speech intelligibility between the forearm flap reconstructed group and adjacent flap reconstructed group (P > .05). There was a significant difference in the result between the T1 and T3 groups (P < .05). The speech intelligibilities of the patients with tumors in anterior tongue or hemitongue were significantly lower than those with tumor in the middle or posterior tongue (P < .05). Patients with preservation of the tip of the tongue or floor of the mouth had higher intelligibilities (P < .05).

CONCLUSION

For the patients after glossectomy within the range of hemitongue, except for the type of reconstruction, the tumor site or excision extent of the tongue followed by the tumor size may be key factors in determining the postoperative articulation intelligibility.

Establishing a reliable protocol to measure tongue sensation

The relationship between tongue sensation and tongue function for speech, mastication and deglutition are growing areas of interest among rehabilitative professionals. To determine the potential effect that sensation has on function, it is imperative that, first, reliable and valid measures of tongue sensation be established. The aim of this study was to develop a protocol to test tongue sensation across a spectrum of sensory functions that included two-point discrimination, light-touch discrimination, thermal sensation, texture recognition, oral stereognosis and taste recognition. Materials tested within each domain respectively included: (i) the MacKinnon-Dellon Disk-criminator, paperclip and caliper; (ii) the Semmes-Weinstein monofilament and cotton wisp; (iii) dental mirrors and glass test tubes; (iv) spheres of textured acrylic resin on rods; (v) acrylic resin forms with differing shapes on rods and (vi) salty, sweet, sour, bitter and neutral solutions. Materials were tested on 40 healthy subjects between the ages of 20 and 55. The results from this study indicated that thermal, texture and taste sensations appear robust for accuracy and discrimination. Two-point discrimination and light touch seem to be influenced by location of stimulation on the tongue and force applied, whereas stereognosis was influenced by stimulus complexity. The results of this study indicate that clinicians may choose instruments as practical as paperclips and test tubes for testing two-point discrimination and thermal sensation, respectively. For the other sensations, it may be important to use more sophisticated instrumentation to control variables of force, surface area stimulated and assessing sensations in graded steps.

Current Options in Head and Neck Reconstruction

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Understand current trends in the treatment of head and neck cancer. 2. Discuss the challenges of reconstructing head and neck defects 3. Understand the different reconstructive options available for specific anatomical regions of the head and neck.

BACKGROUND

Reconstructive surgery of the head and neck is both technically challenging and rewarding. In the past 20 years, significant advances in this field have improved surgical outcomes and patient function. The development and subsequent refinement of microvascular techniques, in particular, have been a major reason for this progression.

METHODS

In this article, the authors review the current options available in head and neck reconstruction. Because a large number of major craniocervicofacial defects result from oncologic resection, the authors have focused their review on this particular subject. By dividing their discussion into different anatomical sites, the authors hope to cover all major aspects of this broad topic.

RESULTS

Free tissue transfer has revolutionized head and neck reconstruction. The most widely used free flaps include the fibula, radial forearm, anterolateral thigh, and rectus abdominis. Restoration of both form and function is the ultimate goal.

CONCLUSIONS

Although defects of the head and neck region present a challenge, successful cosmetic and functional results have been achieved with both local and free tissue flaps. The flexibility of free tissue transfer, however, has dominated this area and continues to be the method of choice for reconstruction of sizable defects.

Sensory reinnervation of a musculocutaneous flap: an experimental rabbit study

Sensory neurotisation of a muscle (sensory nerve transfer to the motor nerve of a muscle) produces muscle sensibility, but not skin sensibility. How to achieve sensation of a musculocutaneous flap remains a challenge to reconstructive microsurgeons. The purpose of our study was to determine if multiple nerve grafts which were placed vertically between the neuromuscular entrance zone of a muscle and a target area of dermis on the overlying skin could improve sensation. Thirty-six gracilis musculocutaneous flaps (18 rabbits) were raised and divided into three groups: group 1 consisted of 12 sensory neurotised gracilis musculocutaneous flaps with five nerve grafts each; group 2 consisted of another 12 sensory neurotised gracilis flaps with 10 nerve grafts each; and the control group consisted of 12 sensory neurotised gracilis musculocutaneous flaps without any nerve grafts. All nerve grafts spanned the distance between the neuromuscular entrance zone of the gracilis muscle and a specified 3 cm diameter area of the skin island. The saphenous nerve (sensory) was coapted to the obturator nerve (motor nerve of the gracilis) in an effort to achieve improved sensation of the skin island in the musculocutaneous flaps. After 6 months, the flaps were individually evaluated using cortical somatosensory evoked potentials (CSSEP) using normal, painful, cold and hot stimuli. One unoperated rabbit was studied as the baseline CSEEP for comparison. Retrograde horseradish peroxidase (HRP) labelling was then performed to evaluate the possibility of newly established neural pathways. Results of the CSSEP testing revealed that flaps possessing 10 nerve grafts (group 2) demonstrated better sensation when compared to flaps possessing five nerve grafts (group 1) or no nerve grafts (control group). Furthermore, retrograde HRP labelling proved that a new neural pathway had been established from the skin island to the dorsal root ganglia of S1 and S2 via the interposed nerve grafts and the sensory neurotised gracilis muscle in groups 1 and 2 rabbits. The control group did not display any sensory regeneration.

[Anatomic study and advantages of the free rectus abdominis flap for head and neck reconstruction]

INTRODUCTION

The main goal of using the free flap is to be able to carry out extensive surgical resection resulting in good functional outcome. The aims of this study were to define the best area for free rectus abdominis harvest and to assess its value in head and neck reconstruction.

MATERIAL AND METHODS

Twenty rectus abdominis flaps were studied in ten fresh cadavers. A review of the literature of the free rectus abdominis flap in head and neck reconstruction yielded the main recipient sites and complications (flap necrosis and postoperative abdominal hernia). A reconstruction was performed after near total glossectomy.

RESULTS

With seven perforators and four cutaneous branches of intercostal nerves, the paraumbilical region is the best area to harvest this flap. The rectus abdominis free flap seems to be adapted for near total glossectomy reconstruction. Previous studies reported that this flap was essentially used for oropharynx and skull base reconstruction. The main complications are flap necrosis (4%) and abdominal hernia (3%).

CONCLUSION

The paraumbilical rectus abdominis free flap is reliable and easy to use with a two-team approach in head and neck reconstruction with moderate donor site morbidity. It is useful for reconstruction of large defects of the oropharynx and skull base. Sensory-motor reinnervation superiority for deglutition in tongue reconstruction still needs to be evaluated.

Swallowing after free-flap reconstruction in patients with oral and pharyngeal cancer

Swallowing and intraoral sensation outcome were investigated prospectively after microvascular free-flap reconstruction. Forty-one patients with a large oral or oropharyngeal carcinoma underwent free-flap surgery usually combined with radiotherapy. The patients completed modified barium swallow, self-rating of swallowing, and 2-point moving discrimination preoperatively and at four time points during the 12-month follow-up period, and a plain chest X-ray one year after operation. Swallowing was impaired with respect to an objective and subjective measure after therapy. Rates for nonsilent and silent aspiration increased during the follow-up. Intraoral sensation deteriorated. Swallowing outcome was not related to sensation. One year after surgery, 86% of the patients ate regular masticated or soft food. Microvascular transfers offer a reasonable option for oral reconstruction. This study does not support the need for sensate flaps. Swallowing problems should be routinely sought and patients rehabilitated during a sufficiently long follow-up with videofluorography regardless of the patient's perception of swallowing.

Functional reconstruction with free flaps following ablationof oropharyngeal cancer

With the development of various reconstructive procedures, most patients who have undergone ablative surgery for oropharyngeal cancer have obtained satisfactory functional results and good quality of life. However, many questions remain concerning methods of obtaining optimal postoperative oral and pharyngeal functions, especially after glossectomy. This review focuses on reconstructive methods after partial glossectomy, hemiglossectomy, and subtotal or total glossectomy and discusses current problems and the possibility of sensory and dynamic reconstruction.

Use of the anterolateral thigh free flap for upper-extremity reconstruction

PURPOSE

The anterolateral thigh free flap (ALTF) first was reported in 1984 and has been used in large series with success for a multitude of clinical purposes. We describe our results with the ALTF in upper-extremity and hand reconstruction.

METHODS

From 1996 to 2003 there were 15 patients who had reconstruction of the hand and upper extremity using the ALTF. The parameters used to assess the outcome of our series included the success rate of the flap as measured by flap survival rate and adequacy of skin coverage, ability to close the donor site primarily or necessity of a skin graft, complications associated with the flap, donor site, and non-flap-related complications such as pulmonary embolism.

RESULTS

Of the 15 patients with an ALTF, 3 (20%) had a musculocutaneous perforator and 12 (80%) had a septocutaneous perforator. Two patients had a neurotized ALTF reconstruction. There were 4 complications related to the flap with 1 complete flap failure. The overall flap survival rate was 93%. The donor site was closed primarily in 8 patients (53%) and with a skin graft in 7 patients (47%). One donor site breakdown occurred.

CONCLUSIONS

Our results show many advantages of the ALTF for upper-extremity reconstruction. Because of its versatility the ALTF is suited ideally for upper-extremity reconstruction and should be considered as part of the reconstructive ladder.

Reconstruction for Total and Near-Total Glossectomy Defects

Reconstruction of total or near-total glossectomy defects has been challenging and the functional outcomes are often disappointing. In this article, the 10-year experience of total or near-total tongue reconstruction at the University of Texas M.D. Anderson Cancer Center is reviewed. The trends of surgical and functional outcomes, length of hospital stay, and choices of flaps and recipient vessels are identified. In addition, the investigators' experience, as well as a literature review, of sensory and motor reinnervation for tongue reconstruction is presented.

Sensory topography of the oral cavity and the impact of free flap reconstruction: A preliminary study

BACKGROUND

The purpose of this prospective randomized study was to (1) assess the computerized pressure-specific sensory device (PSSD) as a tool for measuring oral cavity sensation, (2) establish a topographic sensory map of the oral cavity, and (3) objectively evaluate postoperative sensory recovery of noninnervated oral cavity free flap reconstruction.

METHODS

Twenty-three healthy control subjects were recruited to test four intraoral sites and the volar forearm. Sensory scores were evaluated for consistent trends between an established sensory tool, the Semmes Weinstein Monofilament (SWM), and the PSSD. Sensory control values were then compared with those of 18 patients who underwent reconstruction of the oral cavity with a noninnervated microvascular free flap.

RESULTS

The SWM testing demonstrated the lowest sensory thresholds in the lower lip, followed by the lateral tongue, buccal mucosa, and central tongue. The PSSD also demonstrated the lowest sensory thresholds in the lower lip followed by the lateral tongue; however, the central tongue demonstrated a lower sensory threshold than did the buccal mucosa. The neotongue of patients with noninnervated free flaps demonstrated inferior sensation compared with the native tongue (p < .05).

CONCLUSIONS

We have established normal sensory values for the oral cavity, skin of the volar forearm, and noninnervated free flap tissue within the oral cavity. Although discrepancies exist between the data derived from the SWM and the PSSD, the PSSD represents a reliable, sensitive, and easy method for assessing sensation of the oral cavity. Furthermore, PSSD testing is not affected by saliva or movement.

Traumatic Ulceration Mimicking Oral Squamous Cell Carcinoma Recurrence in an Insensate Flap

We report our experience with a patient who developed an ulcer within a free flap 2 months following resection of an oral squamous cell carcinoma. We discuss this clinical problem and the issues it raised, with particular attention to early tumor recurrence and the restoration of sensation in free-flap reconstructions.

Reinnervated anterolateral thigh flap for tongue reconstruction

BACKGROUND

Total or near-total glossectomy defects are commonly reconstructed with rectus abdominis myocutaneous flaps for coverage. Sensory reinnervation has rarely been performed.

METHODS

Thirteen consecutive total or near-total glossectomy reconstructions were performed in a 12-month period with anterolateral thigh flaps with (n = 8) or without (n = 5) sensory reinnervation to the lingual nerve. Two-point discrimination, Semmes-Weinstein monofilament testing, pain, and temperature testing were performed before and after 12 months of surgery. Speech and swallow functions were assessed with an established grading system.

RESULTS

Innervated flaps had superior sensory recovery to noninnervated flaps in all testing modalities. Postoperative radiotherapy may delay sensory recovery. Swallow function was better in the innervated group. Return of sensation also improves overall patient satisfaction.

CONCLUSIONS

The reinnervated anterolateral thigh flap is a viable option to reconstruct total or near-total glossectomy defects with good speech and swallow functions.

Adipofascial anterolateral thigh free flap for tongue repair

With the advent of microsurgery fasciocutaneous free flaps have become a well known and accepted option for the repair of tongue defects. Many authors have tried to recover tongue function by modifying this approach. An innovative method for the repair of tongue defects using an adipofascial anterolateral thigh free flap is presented in this paper. The results are compared with those of tongue reconstructions implementing traditional fasciocutaneous free flaps performed at our institution. The histological features of the flaps were investigated postoperatively. Although this preliminary report has to be confirmed by further experience, it seems to solve many tongue-reconstruction related problems.

To thin or not to thin: the use of the anterolateral thigh flap in the reconstruction of intraoral defects

The anterolateral thigh (ALT) flap has achieved popularity recently for free-flap reconstruction of intraoral defects following excision of squamous cell carcinoma. We have assessed the feasibility of the ALT flap as a free flap for oral lining and the potential use of the thinned ALT flap in a one-stage reconstruction. We used the ALT flap to reconstruct the oral cavity in 18 consecutive patients between December 2000 and December 2001 following intraoral resection of squamous cell carcinoma. Twelve patients underwent reconstruction using a standard ALT flap, four patients received a thinned ALT flap in a one-stage procedure, one patient received a standard ALT flap in combination with a fibula flap and one patient received a combination of a standard ALT flap and vascularised iliac bone. There were no complications in any of the 14 cases in which a standard ALT flap was used. Two of these flaps were thinned subsequently as secondary procedures. Of the four thinned ALT flaps, one flap failed completely and two flaps experienced partial necrosis. In all but one case the donor site was closed directly with minimal donor-site morbidity. The ALT flap is a versatile flap that can be used in combination with other flaps for more complex defects with minimal donor-site morbidity and is a useful alternative in the armamentarium of the head and neck surgeon. Thinning of the flap is best performed as a secondary procedure, should it be required.

A prospective controlled double-blind trial of great auricular nerve preservation at parotidectomy

BACKGROUND

Earlier reports of the advantages of preservating the posterior branches of the great auricular nerve (GAN) at parotidectomy were conflicting. This prospective study was aimed at clarifying the controversy.

METHODS

Eighty-one patients in a university otolaryngology department were recruited. The posterior branches were preserved whenever initial dissection showed that tumor clearance would not be compromised. Touch-pressure sensation was monitored in predefined territories supplied by the GAN using a Semmes-Weinstein aesthesiometer, preoperatively and postoperatively. Minimal pressure thresholds obtained were compared between the two groups.

RESULTS

Preservation of the GAN was achievable in 69% of patients; sensory deficit was transient. With the GAN divided, measurable sensory depression occurred up to 2 years after surgery. The difference is statistically significant. Patients' subjective assessment of numbness also conformed to these trends. Additional time taken for preservation of the GAN was about 10 minutes.

CONCLUSIONS

The posterior branches should always be preserved if tumor clearance is not compromised.

Have we found an ideal soft-tissue flap? An experience with 672 anterolateral thigh flaps

The free anterolateral thigh flap is becoming one of the most preferred options for soft-tissue reconstruction. Between June of 1996 and August of 2000, 672 anterolateral thigh flaps were used in 660 patients at Chang Gung Memorial Hospital. Four hundred eighty-four anterolateral thigh flaps were used for head and neck region recontruction in 475 patients, 58 flaps were used for upper extremity reconstruction in 58 patients, 121 flaps were used for lower extremity reconstruction in 119 patients, and nine flaps were used for trunk reconstruction in nine patients. Of the 672 flaps used in total, a majority (439) were musculocutaneous perforator flaps. Sixty-five were septocutaneous vessel flaps. Of these 504 flaps, 350 were fasciocutaneous and 154 were cutaneous flaps. Of the remaining 168 flaps, 95 were musculocutaneous flaps, 63 were chimeric flaps, and the remaining ten were composite musculocutaneous perforator flaps with the tensor fasciae latae. Total flap failure occurred in 12 patients (1.79 percent of the flaps) and partial failure occurred in 17 patients (2.53 percent of the flaps). Of the 12 flaps that failed completely, five were reconstructed with second anterolateral thigh flaps, four with pedicled flaps, one with a free radial forearm flap, one with skin grafting, and one with primary closure. Of the 17 flaps that failed partially, three were reconstructed with anterolateral thigh flaps, one with a free radial forearm flap, five with pedicled flaps, and eight with primary suture, skin grafting, and conservative methods. In this large series, a consistent anatomy of the main pedicle of the anterolateral thigh flap was observed. In cutaneous and fasciocutaneous flaps, the skin vessels (musculocutaneous perforators or septocutaneous vessels) were found and followed until they reached the main pedicle, regardless of the anatomic position. There were only six cases in this series in which no skin vessels were identified during the harvesting of cutaneous or fasciocutaneous anterolateral thigh flaps. In 87.1 percent of the cutaneous or fasciocutaneous flaps, the skin vessels were found to be musculocutaneous perforators; in 12.9 percent, they were found as septocutaneous vessels. The anterolateral thigh flap is a reliable flap that supplies a large area of skin. This flap can be harvested irrespective of whether the skin vessels are septocutaneous or musculocutaneous. It is a versatile soft-tissue flap in which thickness and volume can be adjusted for the extent of the defect, and it can replace most soft-tissue free flaps in most clinical situations.

Free flap reconstruction of the sole of the foot with or without sensory nerve coaptation

The authors present a retrospective study on major plantar foot reconstruction to evaluate the role of the free fasciocutaneous flap and the importance of sensory nerve reconstruction in improving long-term results. Between 1995 and 1999, 20 patients with major defects of the sole of the foot underwent free forearm flap reconstruction performed by the senior author (F.S.). Sensory nerve reconstruction was added to this technique in 1997. The age and sex of the patients and the cause, location, and dimensions of their defects were recorded. The patients were clinically and neurophysiologically evaluated at 3, 6, and 12 months after the procedure for the following parameters: flap contour, flap stability, load capacity, walking ability, touch sensation, pain sensation, static two-point discrimination, and thermal sensibility. Dermatomic somatosensory-evoked potentials were also tested at 12 months. Follow-up ranged from 1 to 5 years. Patients were divided into two groups according to sensory nerve reconstruction. Group A consisted of 11 patients with nerve repair, and group B consisted of nine patients without nerve repair. One patient from group A who had an idiopathic neuropathy was excluded from the study because of interference with the reinnervation process. Five more patients (three from group A and two from group B) were lost at follow-up and excluded from the study. The final sample size in each group was seven. Data from both groups were compared and statistically analyzed with the Mann-Whitney test and the Fisher exact test. Long-term results confirmed in all reconstructions long-lasting stability. During the first postoperative year, patients with sensory nerve reconstruction showed better sensibility. The statistical analyses confirmed significant differences between the two groups to be dependent upon surgical technique at 3 and 6 months. Two-point discrimination and dermatomic somatosensory-evoked potentials were recorded. After 12 months, flaps without surgical nerve repair showed progressive improvement of sensitive thresholds, achieving a good protective sensibility, similar to that of the other group, but these flaps never regained two-point discrimination or dermatomic somatosensory-evoked potentials.

Speech after partial glossectomy: a comparison between reconstruction and nonreconstruction patients

PURPOSE

This study was undertaken to compare the articulation intelligibility of patients after hemiglossectomy or minor glossectomy within the hemitongue with or without reconstruction.

MATERIALS AND METHODS

The articulation intelligibility of 19 patients who underwent hemiglossetomy or minor glossectomy within the hemitongue was investigated at least 6 months after surgery with an articulation intelligibility test with 40 sensitive Chinese sounds. Patients were divided into group 1 (those undergoing reconstructive surgery after glossectomy) and group 2 (those not undergoing reconstructive surgery after glossectomy). Defects of the tongue (in group 1) were reconstructed immediately with free radial forearm flaps or pedicled flaps after glossectomy and closed primarily without reconstruction in group 2. The articulation intelligibility scores were compared between the 2 groups.

RESULTS

The mean articulation intelligibility score for group 1 was 77.0% (blade portion glossal sounds), 76.3% (mid portion glossal sounds), and 84.7% (rear portion glossal sounds), and those of group 2 were 94.6%, 92.1%, and 95.3%, respectively. The intelligibility of articulation of group 2 was significantly higher than that of group 1 in blade portion glossal sounds (P <.05), mid portion glossal sounds (P <.05), and rear portion glossal sounds (P <.01).

CONCLUSION

The articulation intelligibility was better in patients not receiving grafts than in those receiving grafts. Reconstruction with flaps, which may interfere with the flexibility and mobility of the tongue, may contribute to articulatory impairment. If speech is the outcome of interest, reconstruction may be unnecessary with hemiglossectomy or other partial (minor) glossectomy within the hemitongue.

Postoperative complications and functional results after total glossectomy with microvascular reconstruction

Microsurgical reconstruction after total glossectomy can greatly improve quality of life; however, postoperative functional results are often unstable, and the effectiveness of total glossectomy remains questionable. To determine the problems of reconstruction after total glossectomy with laryngeal preservation and to examine the functional results of swallowing and speech, 30 patients who had undergone total glossectomy and reconstruction with free flaps were reviewed for this study. The patients ranged in age from 20 to 73 years, and 23 of the 30 had undergone reconstruction with a rectus abdominis musculocutaneous flap. Wider and thicker flaps were designed and transferred and were sutured to suspend the larynx. To maintain physiologic swallowing function after surgery, the extent of laryngeal suspension and cricopharyngeal myotomy was limited. Of the 30 patients, 21 (70 percent) could be decannulated with laryngeal preservation; 20 of these 21 could tolerate a normal/soft/pureed diet, and 1 was limited to a fluid diet. Speech was intelligible in 16 of the 19 patients evaluated. In 9 of the 30 patients, laryngeal function could not be preserved. In four of these nine patients, additional resection combined with total glossectomy caused severe aspiration and recurrent pneumonia. Two patients with preoperative cerebral dysfunction were also poor candidates for laryngeal preservation. Additionally, the transferred flap's lack of bulk in the oral cavity and the advanced age (73 years) of one patient and the poor motivation of another may have contributed to postoperative aspiration. Aspiration occurred in one patient because of local recurrence of a tumor. The presence of preoperative cerebral dysfunction (p = 0.025), resection of the epiglottis (p = 0.005), and postoperative orocutaneous fistulas (p = 0.04) were significantly associated with the failure of laryngeal preservation. However, because of the difficulty of enrolling a sufficient number of patients in the study and the inherent limitations of retrospective studies, multivariate analysis in this study showed that no factors, such as patient age, flap volume, and the type of neck dissection, were significant predictors of laryngeal preservation. Although prospective studies are necessary, the function of individual patients must be assessed so that the study experiences discussed here can be applied to subsequent patients.